I know that Mono Touch enables developing with nearly one source code and deploy to Android, iOs and Windows Mobile. There will of course be 3 projects and some platform related code but I will have important common code in C#.
But I also need my development to work on standard Windows 7 and 8 (non mobile). Can I do this with Mono Touch and I yes what is the development process ?
I think you should check out my answer to this question: Consuming ViewModels in MonoDroid / MonoTouch
In general, you should create a shared class library that will be used on all platforms.
This class library would then be consumed by as many UIs as you need, such as MonoTouch, Mono for Android, WP7, Windows, Metro, etc.