http://www.funbrain.com/brain/MathBrain/MathBrain.html
I also like this game because it's very fun and educational. I used to play this years sgo. I like how you can select your grade level. It's also different that you get to move along a game board. One thing that stands out is that you can get a code and leave. Then, when you want to play again you can type in the code and it will restore your place on the gameboard and your progress.