If you want to build for mobile nowadays, then Android has to be a serious consideration along with iPhone and WinMo development. I've not touched Android at all yet so it's great to see this informative overview of what it takes to get going over at Ze Goggles.

Just a quick post to say that if you want to get going quickly with building games on the iPhone, then the best way is to use a framework. The best one out there is easily Cocos2d as it abstracts away all of the dense Open GLS in a simple to understand object model.