there is this little game on PSN right now that's free to play. it's a small game of distance traveled via a jetpack, and you have to collect coins and finish mission objectives to continue. Jetpack Joyride is an addicting game that seems to suck you in and keeps making you come back for more.
there's a lot of great geek humor in it, very subtle mind you. for example, you can buy a supersaiyan outfit for 9001 coins (IT"S OVER 9000) and there a flying piggy bank (when pigs fly)
my two daughters play it almost everyday, switching out every other time, so the coins keep rolling in to buy stuff. it's a pretty slick game, especially since it's free.