Zuma is pretty cool online game where you shoot colored balls at a winding line of balls. Once you line up 3 balls of the same color they disappear (surprising ah?) and the line shortens.
You need to clear up all the balls before they reach golden skull at the end of the line in order to advance to the next level.
You can either play the game online or download a free copy.
Watch out, this one can be really addicting.
Play the game