Kids (and grown-ups too!) need many opportunities to play around with math; to have fun with numbers and mathematical principles. I'm always on the lookout for some good math games and puzzles and we've recently found a winner in Carston Studios' Math Doodles. (Click on Web Demos to get to the games)
We love all the games there, but our favorite right now is Hydromaze. The Sums Stacker and Number Jump games have also been great for practicing addition facts and money math.
My big complaint with free online math games is that they're usually just glorified flashcards. There might be some fancy graphics and maybe a cool storyline, but they require virtually no creative thought or problem solving. Math Doodles are a refreshing change from the norm. All the games on the site require players to think flexibly to solve the various problems. And they're universally enjoyable. My first graders both love them, I love them, even two-year old Jack loves to try to help figure out the Hydromaze.
The Web Demo games can be played for free, and they also have iphone apps available for purchase for those who like to keep their math games portable.
Go on now, play with your math.