Encyclopedias

Wikipedia
http://en.wikipedia.org/wiki/main_page

Wikipedia is a multilingual, Web-based, free-content encyclopedia project. The name "Wikipedia" is a portmanteau (a combination of portions of two words and their meanings) of the words wiki (a type of collaborative Web site) and encyclopedia. Wikipedia's articles provide links to guide the user to related pages with additional information.
Wikipedia is written by volunteers from all around the world and anyone can edit it.


Encyclopædia Britannica
http://www.britannica.com/

The Encyclopædia Britannica is a general English-language encyclopaedia published by Encyclopædia Britannica, Inc., a privately held company. The articles in the Britannica are aimed at educated adult readers, and written by a staff of about 100 full-time editors and over 4,000 expert contributors. It is widely regarded as the most scholarly of encyclopaedias.