Deep Web Search Engines

To get started, try using a search engine that specializes in scouring the invisible web for results. None of these can search the entire invisible web, but they make some inroads that Google has not as of yet.

1. Clusty — A metasearch engine that combines the results of several top search engines.
2. Intute — A searchable database of trusted sites, reviewed and monitored by subject specialists.
3. INFOMINE — A virtual library of Internet resources relevant to university students and faculty. Built by librarians from the University of California, California State University, the University of Detroit-Mercy, and Wake Forest University.
4. Librarians' Internet Index — A search engine listing sites deemed trustworthy by actual human librarians, not just a Googlebot.
5. Internet Archive — A database of tens of thousands of movies, live music, audio, texts, and home of the Wayback Machine that allows you to find old versions of web pages, over 55 billion.
6. direct search — A list of hundreds of specialty databases and search engines. No longer maintained, but still perhaps the most complete list of the deep web.

Art

Hundreds of other museums all over the world have their own databases. This is just a list of the databases for a few of the most popular. Within these databases are descriptions of the work, its location, and an image of the work.

7. Musée du Louvre — One of the oldest and most famous art galleries in the world. Contains Leonardo da Vinci's Mona Lisa and Alexandros de Antioch's Venus de Milo.
8. Guggenheim Museum — A collection of over 160 classical and new artists, searchable by artist name, title, date, movement, medium, concept, and museum.
9. Smithsonian National Portrait Gallery — A searchable database of more than 80,000 portrait records.
10. The National Gallery of Art — A searchable catalog of all of the museum's 110,000 objects, with images of more than 6,000 available online.

Books Online

There are tens of thousands of classic books with full text available online for free. Some authors whose books are available in full text online include Jane Austen, Charles Dickens, and Fyodor Dostoevsky.

12. The Online Books Page — A searchable database of more than 25,000 English works with full text available for free online.
13. Bibliomania — A searchable database of free online literature from more than 2,000 classic texts.
14. Project Gutenberg — A searchable online catalog of more than 19,000 free books with full text available online.
15. The National Academies Press — A searchable directory of 3,000 free books online and 900 for-sale PDFs.
16. ebrary — A searchable database of more than 20,000 full-text books.

Business

The most accurate quantitative business knowledge often comes from specialty search engines and business directories/databases.

17. Explorit Now! — A portal allowing searchable access to numerous business journals and databases.
18. AAAAgencySearch.com — A searchable database of advertising agencies from the American Association of Advertising Agencies.
19. Agency ComPile — A searchable database of advertising and other marketing agencies.
20. Kompass — A business to business search engine.
21. GPO Access Economic Indicators — A portal to economic indicators from January 1998 to present.
22. CBDNet — A searchable database of materials published by the US Department of Commerce.
23. Hoover's — A searchable database of businesses.
24. ThomasNet — An industrial product search directory.
25. SBA Loan Data — A database of loan program approval activity from the Small Business Administration.
26. GuideStar.org — A searchable database of non-profit organizations.

Consumer

For consumers, authoritative product reviews and pricing information often times are hidden in the deep web or among subscription-based reports.

27. US Consumer Products Safety Commission Recalled Products — A database of recalled products, sortable by company name.
28. Melissa Data — A directory of complete demographic data, sortable by ZIP code.
29. Kelley Blue Book — A guide to pricing new and used vehicles.
30. Edmunds — Another guide to pricing new and used vehicles.
31. Consumer Reports $ — A guide to consumer product reviews, including cars, appliances, electronics, computers, personal finance, travel, and more.

Economic and Job Data

A wealth of information regarding microeconomic and macroeconomic data is available from government sources and other organizations.

32. EUROPA Press Release Database — A searchable database of press releases distributed by the European Union.
33. FreeLunch.com — A searchable directory of free economic data.
34. Bureau of Labor Statistics — A directory of job-based and consumer economic data from the US Department of Labor.
35. Salary Wizard Calculator — A tool that shows national average salaries adjusted by location for different jobs.
36. Economagic — A free economic data directory containing over 200,000 data files.
37. Penn World Tables — A database of purchasing power parity and national income data for 179 countries for the years 1950-2000.
38. America's Job Bank — A searchable database of jobs and resumes.
39. USAJOBS — A searchable database of federal government jobs.
40. Regional Economic Conditions (RECON) — A database of economic data available by state, county, and MSA.

Finance and Investing

A variety of web-based investment analysis tools and financial statistics can only be found in the deep web.

41. Bankrate.com — A directory of interest rates for different types of loans, mortgages, and savings accounts.
42. InvestIQ — A database of market data from different world regions.
43. BigCharts — A searchable database of quotes and performance charts for different stocks and mutual funds.
44. SmartMoney.com Tools — A portal of different stock analysis tools.
45. NASDAQ Trader — A database of trading data from the NASDAQ stock exchange.
46. SEC Info — A searchable database of EDGAR SEC filings searchable by name, industry, business, SIC code, area code, topic, CIK, accession number, file number, date, ZIP code, and more.
47. EDGAR Online — A database of EDGAR SEC filings searchable by ticker or company name.

General Research

These are good places to start researching for background knowledge on any topic. The subscription-based databases will help intensify any research by scouring numerous scholarly journals.

48. GPO's Catalog of US Government Publications — A searchable database of federal publications, with links to those available online.
49. Smithsonian Institution Libraries — A collection of 20 libraries from the world's largest museum complex.
50. The National Archives — A list of all of the National Archives' research tools and databases.
51. HighWire Press — A searchable catalog of the largest repository of free full-text, peer-reviewed content, from over 900 different journals.
52. Education Resources Information Center (ERIC) — A catalog of more than 1.2 million bibliographic records, providing links to the full text where available. Sponsored by the US Department of Education and the Institute of Education Sciences.
53. Encyclopædia Britannica — The authoritative encyclopedia searchable with full text online.
54. Topix.net — A news search engine.
55. Internet Public Library — The Internet's public library. Fully searchable.
56. San Francisco Public Library - A list of all of the databases offered to SFPL library card holders. Not a California resident? This is just one example of many such local public libraries that offer similar services.
57. Xrefer $ — A searchable database of 236 titles and over 2.8 million entries.
58. LexisNexis $ — The world's largest collection of public records, unpublished opinions, forms, legal, news, and business information. Over 35,000 individual sources are searchable with full-text available online.
59. Forrester Research $ — An independent technology and market research company, publishing in-depth research reports on a variety of subjects.
60. Factiva $ — A searchable collection of over 10,000 individual sources.

Government Data

The United States government publishes data on a variety of subjects, some of which is derived from census data or CIA findings.

61. Copyright Records (LOCIS) — A database of copyright records, searchable by documents, serials, and multimedia (including books, music, films, sound recordings, maps, software, photos, and art).
62. American FactFinder — A repository of aggregate census bureau data searchable by city, county, or ZIP code.
63. FedStats — A gateway to statistics from over 100 US federal agencies.
64. United States Patent and Trademark Office — A database of patent full-text and full-page images.
65. Historical Census Browser — A data bank of historical US census data dating back to 1790 compiled by the University of Virginia.
66. Geospatial One Stop — A searchable database of geographic data, displayable on maps.
67. Grants.gov — A database of grant opportunities, searchable by keyword, funding opportunity number, or CFDA number.
68. Technology Opportunities Program Grants Database — A database of technology grants, searchable by keyword, state, and year.
69. United States Government Printing Office (GPO) — A search engine for mutliple government databases, including US budgets, campaign reform hearings, code of federal regulations, congressional bills, unified agendas, and more.
70. CIA Electronic Reading Room — A searchable database of declassified CIA documents.
71. POW/MIA Databases and Documents — A datbase of POWs and MIAs information.
72. ZIP+4 Lookup — A database of US ZIP codes and ZIP+4 codes, searchable by city or address.

International

Data on international economic indicators and demographics are available from US government agencies and international organizations such as World Bank.

73. International Data Base (IDB) — A computerized data bank of statistical tables and demographic information for 228 countries and areas.
74. FIRST — A database of military aggression and weapons holdings.
75. Economics of Tobacco Control — A database of information regarding tobacco usage and policy in over 180 countries.
76. Country Indicators for Foreign Policy — A directory of statistical tables indicating different countries' foreign policies.
77. World Bank Data — A database of key development data and statistics for different countries and worldwide groups.
78. CIA Factbook — A reference material published by the CIA, containing information on every country in the world.
79. US International Trade Statistics — A database of international trade statistics, searchable by country or type of good.
80. US Foreign Trade Highlights — A database of information on US international trade in goods and services.
81. Energy Information Administration International Energy Data and Analysis — A data bank of energy balances sorted by country.

Law and Politics

Information on Congressional law and other legal and political matters are available online from universities, independent organizations, and the US federal government.

82. THOMAS (Library of Congress) — A searchable database of legislative information from the Library of Congress.
83. Law Library of Congress — The largest collection of legal materials in the world, containing over 2 million volumes.
84. Global Legal Information Network — A searchable public database of laws, regulations, judicial decisions, and other legal sources.
85. FindLaw — A free legal database with searchable collections of cases and codes, legal news, and an online career center.
86. Office of Postsecondary Education Security Statistics — A searchable database of college campus crime statistics, sortable by institution type, instructional program, or campus.
87. Bureau of Justice Statistics — A directory of legal and judicial statistics, ranging from crime to law enforcement to courts and sentencing.
88. The Avalon Project at Yale Law School — A searchable database of documents in law, history, and diplomacy.
89. US Congressional Documents and Debates, 1774–1873 (Library of Congress) — A directory of historical Congressional records, bills, statutes, journals, and debates from LOC's American Memory.
90. Lobbying Database — A searchable database of firms who have spent lobbying money from 1998.
91. Legislative Activities — A directory of the House of Representatives' bill summary, status, and text, public laws, and roll call votes.
92. Project Vote Smart — A database of government officials and election candidates, searchable by last name or ZIP code.

Library of Congress

The Library of Congress (LOC) is the largest library in the world and offers catalog descriptions and some full text and images of many of its 130 million items.

93. Library of Congress — A searchable catalog of the world's largest library, containing over 130 million items.
94. Library of Congress Digital Collections — A searchable database of the LOC's items that have been digitized and fully available online.
95. Library of Congress Prints and Photographs Reading Room — A searchable catalog of the Library of Congress' prints and photographs. Results include thumbnails of the items.
96. Library of Congress Online Catalog — The LOC catalog, searchable by title, author, subject, keyword, call number, ISBN, and more.
97. American Memory — The LOC's digital record of American history.
98. Sound Online Inventory and Catalog (SONIC) — A portion of the LOC's audio collection, searchable by name, title, subject, and keyword.

Medical and Health

Scholarly medical journals as well as government agencies and independent organizations offer a variety of statistical data and other information regarding medicine and health.

99. PubMed *NEW ADDITION* — A service of the U.S. National Library of Medicine that includes over 16 million citations from MEDLINE and other life science journals for biomedical articles back to the 1950s. Includes links to full-text articles and related resources.
100. Department of Health National Research Register — A searchable database of records of ongoing or completed project funded by or of interest to the UK's NHS.
101. National Institutes of Health — A searchable encyclopedia of health topics.
102. American Hospital Directory — A free searchable directory of US hospital information.
103. Globalhealthfacts.org — A data bank of world health information, sortable by country, disease, condition, program, or demographic.
104. Centers for Disease Control and Prevention Data and Statistics — A data bank of statistical health information compiled by the CDC.
105. New England Journal of Medicine $ — A scholarly medical journal with full text of current and past issues available online.

Science

Science journals and databases are searchable through specialty search engines, while real-time geological data is available from the USGS.

105. ScienceResearch.com — A portal allowing searchable access to numerous scientific journals and databases.
106. Science.gov — A searchable gateway to authoritative science information provided by US government agencies.
107. WebCASPAR — A database of science and engineering statistical data resources.
108. The Complete Work of Charles Darwin — All of Charles Darwin's published texts, fully searchable and available online.
109. USGS Real-Time Water Data — A map of the United States showing real-time streamflow and water quality data of the nation's rivers and reservoirs.
110. USGS Earthquake Hazards Program — Maps of California, Nevada, the United States, and the World, showing real-time earthquake data.
111. Ask.com Recent Earthquake Activity — An interactive map of the world, showing real-time earthquake data.
112. IEEE Publications $ — For engineers, this is a database of over 1.4 million documents from the Institute of Electronics and Electrical Engineers.

Transportation

Real-time aviation data as well as historical and current transportation safety information is available from different US federal government agencies.

113. FAA Flight Delay Information — A map of the United States with flight delay information from the nation's largest airports.
114. NTSB Accident Database and Synopses — The National Transportation Safety Board's database of aviation accidents, ranging from 1962 to present.
115. NTSB Aviation Accident Statistics — A directory of aggregate aviation accident statistics from the National Transportation Safety Board
116. National Highway Traffic Safety Administration — A database of car and car part defects, searchable by item number or car make and model.
117. SaferCar.gov — A database of crash test safety ratings for all automobiles since 1990.
118. fboweb.com — A real-time flight tracking service, with support for Google Earth.
119. FlightAware — Another free flight tracking service, complete with history, graphs, and maps.

A special thanks to Gary Price at ResourceShelf for his thoughtful suggestions.