I just came across this:
http://monogame.codeplex.com/I had a quick peek, and it look very cool. There's just about nowhere that you can't make a game for!
FOR DEVELOPMENT
iOS - Mac OS X, MonoTouch, MonoDevelop
Android - Mac OS X or Windows, Mono for Android, Mono Develop or Visual Studio
MacOS X - Mac OS X 
, MonoMac, OpenTK, MonoDevelop
Windows - Windows, Mono, OpenTK, MonoDevelop or Visual Studio
Linux - Linux, Mono, OpenTK, MonoDevelop
And they have more coming!
What is MonoGame?
MonoGame is an Open Source, OpenGL implementation of the Microsoft XNA 4 Framework. Our goal is to allow XNA developers on Xbox 360, Windows & Windows Phone to port their games to the iOS, Android, Mac OS X, Linux and Windows 8 Metro. PlayStation Mobile development is currently in progress.
Anyway, thought it looked cool and thought I'd pass it along for anyone that's interested in writing a game.
