Tying in with Facebook game, Cityville, this app involves helping Santa to rebuild the North Pole. A blizzard has scattered the elves and you need to tempt them back with a great town and save Christmas. It's a good game, just watch out for in-app purchases.
Another Zynga Facebook favourite becomes mobile with the launch of Cityville Hometown. Build your city, interact with friends, complete goals and collect rewards. Visit your friends towns and help both your economies grow. The game is separate from the Facebook version but a whole new town just means more fun!