Encarta
Msn encarta: your gateway for interactive learning on the web.
http://www.encarta.com/
Funk and Wagnalls
Funkandwagnalls.com
http://www.funkandwagnalls.com/
The Encyclopedia Britannica
Explore the updated online encyclopedia from encyclopaedia britannica with hundreds of thousands of articles, biographies, videos and photos along with access to the britannica student encyclopedia, britannica concise encyclopedia, and merriam-webster's dictionary & thesaurus.
http://www.britannica.com/