The WPF3D team have delivered one of the coolest features yet: Fully interactive 2D controls and content rendered in your 3D scene.
Interacting with 2D on 3D in WPF
Here's a taste of what's possible:
Interactive 2D content rendered on a 3D object.
This shows a Button and a TextBox wrapped onto a sphere. The 2D controls behave exactly as you would expect, with hit testing, mouse capture, and everything. Very sweet.
The enabling code is free for download at CodePlex, as the 3D Tools for the Windows Presentation Foundation.