Anyone who is looking for fun games for the iPhone, iPad, or iPod Touch should definitely check out The Square Root Game. It's a great game to play with your friends, kids, or on your own. It combines, math, puzzles, and competition into one ridiculously amazing app. It's been my favorite game for a while now.
Cool - I'll check it out. What about some of the more challenging math games - what are the good places to find those?