Wikipedia

Online encyclopedia covering every topic you need. Can be edited by anyone at any time. In almost every language.

http://www.wikipedia.org/

Encyclopedia Britannica

Encyclopedia Britannica is the online version of one of the world's most famous reference tools. While parts of the website requite a subscription, there is still a great deal of information to be found here. The website has a quote of the day, featured article (which can be sent to readers daily by email) and fun quizzes to expand your mind.

http://www.britannica.com/

Symbols.com

An online encyclopedia that explains over 2,000 Western signs and symbols. If you are looking for a particular symbol, you can use the search function or enter the graphic characteristics of sign. Much of the site's content can also be purchased as a book.

http://www.symbols.com/