Pleased you liked the site. Also have a look at the addition in the speed math game. They start out really easy, but they get harder and it's a great mental math workout when you can do 1-2-3 steps in the calculation (add 2 times 2)
www.mathsisfun.com/games/speed-math.html Perhaps you can come up with some home-made worksheets that would suit his current level?
If you're looking for more extension, try the games at
www.fun4thebrain.com/addition.html There's a range of games that suit girls and boys and they're available for all operations (+ - x /) My girls currently LOVE Wade's workout world, especially for multiplication...
Enjoy! jojo