Online version of the complete reference work along with dictionary, atlas, links, magazines, historical documents, audio, video, images, and 3D photographs. Requires free temporary registration with option to buy continued access for full articles.

Reference source with several hypertext linked entries covering a broad variety of subjects.

Electronic encyclopedia with its own content as well as over 10,000 links to the best reference sites on the Internet.

Browsable online version of the 1911 edition of the Encyclopaedia Britannica.

Over 50 'How Stuff Works' articles.

Offers articles from the Columbia Encyclopedia and Britannica Concise Encyclopedia.

User edited encyclopedia based on Wiki software. Contains articles, information on editing, and a list of differences between this encyclopedia and Wikipedia.

Offers articles from on the 11th edition Encyclopedia Britannica, and from the Crystal Reference Encyclopedia. All articles are searchable and alphabetized.

Provides complete text of Encyclopaedia Britannica with search capabilities, related links, and multimedia enhancements. Full text for subscribers only; free trial available.

Approximately 14,000 entries on topics including art, geography, literature, philosophy, religion. Originally published in 1907.

Featuring 28,000 short articles.

Searchable quotations site, provided in electronic format by Project Bartleby at Columbia University.

Includes a world atlas, dictionary, thesaurus, multimedia collection, and homework tools.

"A subset of the content (concise set) is provided for free, the access to the rest of the Hutchinson Encyclopedia requires subscription."

User-contributed online encyclopedia intended for people whose first language is not English.

Online dictionary, Columbia Encyclopedia, and almanac reference.

Links to on-line Smithsonian resources and answers to frequently asked questions from A to Z.

Peer-reviewed encyclopedia from Google. Articles are written by named contributors.

A free encyclopedia with millions of articles contributed collaboratively using Wiki software, in dozens of languages.