Encyclopedias
Encyclopedia - Britannica Online
http://www.britannica.com/
Encyclopedia.Com
http://www.encyclopedia.com/
Infoplease: Encyclopedia, Alamanac, Atlas, Biographies, Dictionary, and Thesaurus
http://www.infoplease.com/
Ref-Desk.Com
http://www.refdesk.com/
Wikipedia
http://en.wikipedia.org/wiki/Main_Page
Dictionaries & Thesaurus
Dictionary.Com
http://dictionary.reference.com/
Merriam-Webster
http://www.merriam-webster.com/
OneLook Dictionary Search
http://www.onelook.com/
Thesaurus.Com
http://thesaurus.com/