The Homework Center - contains a great deal of reference material for research, it is a free site, but there are ads you will have to deal with.
Discovery Homework - Here is the discovery channel's site to help with homework.
Classhomework.com - This is a free site that has many resources to help with homework.
Homework Help - Contains step-by-step lessons to help with many homework dillemas, it is a pay site
though. You can get a free membership for a day!