As someone who has worked on Managed DirectX,Goblin was a nice Window System(3D UI Controls) which can be found at: http://www.cs.columbia.edu/~eaddy/goblin/
But it now supports XNA and i would like to share this open source project with you.
You can download it from:
http://goblinxna.codeplex.com/
GoblinXNA
Goblin XNA is a platform for research on 3D user interfaces(which i was working on,too) You must have a look at it
Join the conversation! Your thoughts help the community grow.