Addition and Subtraction
Nasa Blast Off Addition Game
This game is addicting. I know this because I found myself playing it for about 30 minutes. The website gives you the sum and your job is to use the numbers on the grid to create that number. You can use as few or as many numbers as you wish. It also times you to see how fast you can clear the board by creating different addition problems.
http://www.nasa.gov/audience/forkids/kidsclub/flash/games/levelthree/KC_Blast_Off.html
http://www.nasa.gov/audience/forkids/kidsclub/flash/games/levelthree/KC_Blast_Off.html