KidSlate for iPad
There are already a ton of great drawing apps out there for the iPad, so why make another? Because my daughter (who was 2 at the time) would accidentally zoom or pan, or have to ask for help changing to a new color.
Realizing the UI and feature set of all the apps I had seen to that point weren't what a toddler needed, KidSlate was born, with it's biggest feature being a complete lack of features.
Easy and simple for kids who just want to draw. Best of all, it's free.
(KidSlate is currently under AppStore review)