This week I did awesome stuff with MonoGame. I can't talk about the project, but I'm blown away with how good MonoGame is, especially for Windows 8-based devices. If you're a fan of XNA (and if you're not, you should be), then you should really pick MonoGame and have a play.
I'm still contemplating open sourcing my Unity-like XNA/MonoGame framework. I'm not sure what's holding me back, really. It is quite nerve wracking making your code open.