Built for me to use for this LD I have started work on RapidXNA 2.0 (which I put the design of onto paper a while back) which has the current functionality of RapidXNA 1.0 (still in Beta, though only because I have yet to test the Xbox 360 build still). The new version is in Alpha due to the fact that it contains only rewritten old features, and none of the new features (like a scripting engine that I kinda hope to finish at some point), but should suitably port between Windows, Windows Phone 7, and Xbox 360 (relying on the fact that I hope the Xbox 360 .dll works).
Simply put my aim with RapidXNA was to make it so I could port between those 3 platforms with only minimal code changes, and in the process I decided I should share it with everyone.
You can get hold of the preview here: http://rapidxna.codeplex.com/releases/view/86321
Should I get enough time, I would like to extend RapidXNA 2.0 to work on every platform supported by MonoXNA as well (giving access to porting to Mac and Linux), but for now, the above 3 should hopefully suffice.