We have been using a pod of ipads for 20 minutes a day during math class for a few weeks now. Each student has a day of the week that is their iPad day. During this time they can play ANY game in my math folder I have created. After 2 weeks it seemed to me that all the kids were choosing the same apps all the time. They were great apps, but I had so many apps that no one was exploring.
One day we hooked the iPad up to the lcd and decided to try out 5 new apps together. Our great find was Arithmetic Invaders! It is a counting game arcade style. As you progress through the levels the counting switches to counting backwards, then to addition and eventually multiplication! The kids LOVED it!
And it's FREE!