I found some cute games at: http://www.teach-nology.com/web_tools/games/. Most of them aren't very educationally sound, but you should try out the Lemonade Stand game. I think it would be great for elementary and middle school math. I played and actually made money, but for kids they have to figure out how much inventory and supplies to buy before the lemons spoil and the ice melts, and how much to charge on a rainy day vs. a sunny day. I had fun, but then again, I'm easily amused.