BrainPOP http://www.brainpop.com
Ed Heads http://www.edheads.org
PBS Kids http://www.pbskids.org
Fun Brain http://www.funbrain.com
I Know That! http://www.iknowthat.com
Gamequarium http://www.gamequarium.com
MysteryNet - Kids Mysteries http://kids.mysterynet.com/
Learning Games for Kids http://www.learninggamesforkids.com/
The Kidz Page http://www.thekidzpage.com/learninggames/index.htm
Cool Math http://coolmath.com/