Project Description
XnaTouch is a free implementation of the XNA Framework for MonoTouch. Your goal is help the port of Zune games for the IPhone / Ipod Touch (and vice versa).
See XnaTouch in action here: http://www.youtube.com/watch?v=8iDtHy36E5k and here: http://www.youtube.com/watch?v=SKk7RChXxzE

Creating Games with XnaTouch

First, add a new file to your project with a code like below:

using MonoTouch.Foundation;
using MonoTouch.UIKit;
using XnaTouch;
using XnaTouch.Samples;
using XnaTouch.Samples.Storage;

namespace XnaTouch.Samples.Storage
{
	[Register ("AppDelegate")]
	class Program : UIApplicationDelegate 
	{
		private Game1 game;

		public override void FinishedLaunching (UIApplication app)
		{
			// Fun begins..
			game = new Game1();
			game.Run();
		}

		static void Main (string [] args)
		{
			UIApplication.Main (args,null,"AppDelegate");
		}
	}
}

Then, add all of your source files from your zune game to your iphone application. You can add these "as link" if you want to share them with both XNA and XnaTouch and replace Microsoft.Xna.Framework with XnaTouch.Framework everywhere in your code.
That's it. Have fun!

A good amount of the code, especially things like Vector2 and math classes come from the Mono.Xna http://code.google.com/p/monoxna/ library and SilverSprite project http://silversprite.codeplex.com. Thanks guys!