We're doing some serious games interface work. Games allow unique new interfaces, but we also want to avoid having to reimplement traditional 2D controls, we want to leverage the years of refinement to windows controls.
How would we go about hosting and rendering .NET controls in a '3D' context? 3D in the sense of, eventually they will have to go through the game engine/opengl, but this could easily just be by painting the control to a texture and putting a textured quad on the interface.
Perhaps you want to look at something like the WPF 2D on 3D work that the WPF3D team was working on. What they did was take WPF GUI controls and mapped them onto a 3D surface like putting an image on a 3D postcard, or taking a world map and wrapping it around a sphere. The user can still interact with these controls as well, like the ability to drag/select a "rectangular" area on the sphere that follows lat/long lines. Pretty cool.
The code is available on CodePlex, but beware, it's released under the Ms-LPL license, which I don't believe is a real free software license. It limits its use only to Windows operating systems. Not sure if that's a concern for you.