http://www.allmath.com/

 This site has flash cards and links to other sites for games, math humor, worksheets, math help and more.

 http://www.aplusmath.com

 This site has basic facts flash cards and a game room, worksheets, multiplication table practice and more.

 http://www.mathfactcafe.com

 This site has a pencil next to pre-made cards so kids can do the facts and have the computer check them.  Kids can print them out and also put in their own numbers and make their own worksheets.

 http://www.funbrain.com

 This site has easier to harder addition and subtraction computation and problem solving. It also has language and grammar skills activities

 http://www.coolmath4kids.com

 This site has a wide range of topics and will give you step-by-step instructions

 http://www.learningplanet.com

 This site has games by grade level but with advertisement and a subscription

 http://www.gamequarium.com

 This site has math activities for K-6

 http://www.SETGame.com

 This is a card game to build students’ visual thinking and pattern skills in math.  Commercial, but does have some great free puzzles

 http://www.math.com

 Good resource of how to do problems

 http://www.mathcats.com

 This is an interactive fun site

http://www.figurethis.org

This site gives you ideas for fun hands-on math activities.  Good for upper grades

http://abcya.com

Loads of math games for K-5 as well as games for reading and language arts