FunBrain - Math Baseball This site lets you choose addition or subtraction to play interactive baseball. The playing levels are as follows: easy works with ones, medium works with tens, hard works with hundreds, and super brain works with thousands.
Math Mayhem This interactive game is played with other people on the Internet. The game can be played with addition or subtraction. The game lasts one minute, and you answer as many questions correctly as you can in that time. Your score is posted with the other players' scores.