We posted a story about the Tetrius Puzzle Game Magnet, but perhaps it's more fun just to make your own. Geek Crafts tells us what you'd need:
* wooden cubes - $2.99 at Michael’s for 42 cubes
* glue - I used some wood glue I had on hand
* magnetic adhesive sheets - $1.00-$1.50 at the dollar store or Michael’s - I used some I had on hand
* spray paint - could be $1.00 per can if you have to buy them - I used paint I had on hand
http://geekcrafts.com/howto-tetris-magnets/ - Thanks Geek Crafts!