http://www.worldbook.com
2. Wikipedia
http://www.wikipedia.com
3. Encarta Online
http://www.msn.com
4. Encyclopedia.com
http://www.encyclopedia.com
5. Britannica Online
http://www.britannica.com
6. Hutchinson Online Encyclopedia
http://www.bt-ern.co.uk
7. EncycloZine
http://www.encyclozine.com