Put together by the University of Michigan library, the Government Documents Center is an exhaustive database of U.S. government statistics and factual documents.
3000 years of world history presented interactively via timelines, graphics, and maps. Click on the time period you're interested in, and then use the menus on the left and the right to manipulate your data.
Search through comprehensive medical database at the Merck Medical Library, an exhaustive index of medical information culled from the Merck series of health resources for both medical professionals and laymen.
14. Library Spot
Library Spot is a reference utopia. You can browse a list of libraries online, newspapers, poetry, archives, maps, current events, dictionaries...you name it, you can probably find it at Library Spot.
Thousands of historical articles, links, and ebooks on historical topics ranging from Africa to World War II.
16. Medline Plus
From the US National Library of Medicine and the National Institutes of Health; searchable indexes of searches pre-forumulated with information, drug resources, medical encyclopedias, interactive tutorials, and current medical news.
The Library of Congress, one of the largest American cultural repositories, has placed their incredible collection of records online via the Library of Congress Online Catalog. According to the Library records, there are over 14 million documents here, including books, serials, computer files, manuscripts, cartographic materials, music, sound recordings, and visual materials.
Over 7000 articles related to anything mythology: Greek, Roman, Norse, Celtic, Native American, and more. The mythology sections are divided into geographical regions, so you can search via country, plus, there are special gallery sections: heroes, genealogical information, and more.
OneLook is a meta search dictionary engine, indexing over 1000 different dictionaries at the time of this writing. You can use OneLook not only for simple definitions, but also for related words, related concepts, phrases that contain a certain word, translations, and more.
If you want to research an auto, Edmunds is the place to do it. You can find information here on both new and used cars, car reviews, industry news, auto shows, local car dealerships, glossary of terms, and savvy auto advice.