This website has the funniest and most fun math games ever. You "win" fantastic prizes, which you can print out, such as a reversible cow suit with working udders, a full color map of the Antarctic (plain white sheet of paper) and a ton of sand.  The games have three difficulty levels and there are about 15 different skills to practice. They are really funny! The only request I have is if you live in the town where I teach, don't let your kids see this. I want them to be delighted and surprised when we do it in school!  For ages about 10 to about 16.