Free homework helpers and fun learning games for all subects:

ABCya elementary subjects divided by grades k-5

funbrain math and reading focused area for grades k-5

Highlights Kids magazine favorite activities for grades k-5

National Geographic Kids exploration for grades k-8

Enchanted Learning themed activities for grades k-8

TIME for kids engaging news for grades 1-8

Exploratorium science site for grades 1-12

How Stuff Works interactive knowledge for grades 5-12