B.J. Pinchbeck's Homework Helper
http://www.bjpinchbeck.com
Incredible site with over 500 references in various topics like Art, Computer Science, Current Events, English, Foreign Languages, Health and P.E., History, Math, Music, Reference, Science, Search Engines, and Social Studies.  This site has won over 100 awards!  It was put together by an eleven year old boy and his father; however, there are many sites that will help any college student at levels from remedial through advanced. 

Resources by Topic
http://ollie.dcccd.edu/Services/StudyHelp/default.htm
Extensive listing of web sites for everything from ESL, English, and math to sites to help you learn how you learn.

Santa Ana College WEB SCOUT
/academic_progs/sacacc/webscout/
A very useful site for educators with relevant links to a variety of subject topics.