Tap Zoo is a good app for the iPhone/iPod Touch. You can go to the app store and get it for free. In this game what you do is you try to make a zoo full of many animals and the more you play the better and higher you’ll go. You start out on level 1 with 300 coins. You can get up to very high levels and many coins to buy more animals and land. The better your zoo gets the more people will come to it and the more interesting the game gets. This is very addicting and you can take it with you anywhere.
Here are some cool zoos that people have made with it:
Here is a full review video on this app which I do not own: