Encyclopedia.com
Free resource offers more tens of thousands of articles from multiple sources.
http://www.encyclopedia.com/

Encyclopaedia Britannica
Provides complete text of Encyclopaedia Britannica with search capabilities, related links, and multimedia enhancements. Free trial available.
http://www.britannica.com/

TechEncyclopedia
Contains descriptions and definitions of more than 14,000 computer terms and concepts.
http://www.techweb.com/encyclopedia/

Children's Encyclopedia of Women
Collection of articles about famous women written by third and fourth grade students.
http://www2.lhric.org/pocantico/womenenc/womenenc.htm

EncycloZine: Learning Fun!
EncycloZine is a concise illustrated encyclopedic portal covering a wide range of topics in the arts, humanities, sciences, and technology. It also features games, puzzles, quizzes, and a multimedia gallery.
http://encyclozine.com/

World Book Encyclopedia
Offers in-depth information on a variety of subjects and educational activities for children.
http://www.worldbook.com/

Spartacus Educational
British online encyclopedia focuses on historical topics. Articles are geared toward students.
http://www.spartacus.schoolnet.co.uk/

Columbia Encyclopedia - 6th edition
Comprehensive online encyclopedia and database of over 51,000 entries.
http://www.bartleby.com/65/

Instrument Encyclopedia
A guide to more than musical 140 instruments from all parts of the world. Includes photographs and descriptions.
http://www.si.umich.edu/chico/instrument/

MSN Encarta Encyclopedia
Includes a world atlas, dictionary, thesaurus, multimedia collection, and homework tools.
http://encarta.msn.com/

How Stuff Works
Articles explain how hundreds of things work, from elements of the human body to space-age technology.
http://www.howstuffworks.com/

Bartleby.com Reference
Reference site allows you to search over the Columbia Encyclopedia, the Encyclopedia of World History, fact books, thesauri, quotes, and more.
http://www.bartleby.com/reference/

wordIQ.com
An online encyclopedia with more than 400,000 pages of content.
http://www.wordiq.com/encyclopedia.html

Open Site
A volunteer-run open content encyclopedia, inspired by the Open Directory Project.
http://open-site.org/

VetCentric Encyclopedia
Find articles on animal health care topics ranging from behavior and preventive care to common and not-so-common diseases.
http://www.vetcentric.com/reference/encyc.cfm

Wikipedia
Free volunteer-edited encyclopedia with over 2.1 million articles.
http://en.wikipedia.org/wiki/Main_Page

2007 Wikipedia Selection for schools
Selection of Wikipedia articles chosen and checked for accuracy.
http://schools-wikipedia.org/

Encyclopedia Smithsonian
Links to online Smithsonian resources and answers to frequently asked questions from A to Z.
http://www.si.edu/Encyclopedia_SI/