Thanks for the suggestions riverreal. I'll have to check these out. Is there a particular one that you like most, or have heard works best?
You had better choose a tool that accommodates your likes.
If you are a beginner I recommend to DO NOT start with C++. So we can discard cocos2d-x and marmalade SDK.
If you want programming we can discard Corona SDK.
Particle SDK looks a little bit complex.
Mono solutions looks good for you. It works with C# and it supports android, iOS, windows, linux, mac...
PhoneGap is a mobile aiming framework, so it also is a good option.
I'm not passionate with mobile development so I don't have much experience.
I think you should wait for a better answer from a experienced mobile developer.