Hola! I just released a public version of my XNA based 2d game framework and example projects. It's done with C# and should be totally monogame compatible.
Documentation is still under works, but check out the sample projects for more info. The Framework itself is mostly documented (but needs improvement).
It provides atleast
- State management
- Sprites, animated and not
- Buttons, Menuentries
- Parallax Backgrounds
- Input management
- Physics through Farseer Physics Library
Go dig if you want. Check out the SmithShooter example project (VS2010 and 2012 projects available)...