This site has large amounts of games by subject area http://www.funschool.com
Interactive site with flash cards, games, and worksheets to help kids improve math skills http://www.aplusmath.com
Play free online games in all subject areas. http://www.funbrain.com
Grades K-12 http://coolmath4kids.com
Grades K-8 http://www.aaamath.com
Grades 1-5 http://wwwscweb4free.com/elementarymathgames.htm
Fun math games and activities http://www.mathcats.com
Grades 1-5 http://www.scweb4free.com/elementarymathgames.htm
Ages 3-12 http://www.prongo.com
Grades 3-5 http://www.facthound.com
Math games and tutorial videos http://www.mathtv.org
Solve problems step by step http://www.mathway.com
fun games!!!! http://www.playkidsgames.com