Hexapies is a great little "paint the board" puzzle game. You are first given a board full of colored splats. By throwing colors of pies at the board, you cause the splats to merge into a larger "meta-splat". Once the board contains one giant splat of one color, you win. Then you get a slightly more difficult board and a few more pies to throw.
The game is quick to play and is very easy to learn. The game includes high score tables as well as "zen" modes where you try to splat as many boards as you can with unlimited pies. Have fun!