Direct3D 10 and 11 API now natively supported by Linux via Gallium3D
Unlike Wine, this implementation of Direct3D under Gallium3D is an actual, native port of the DirectX APIs. There's no emulation involved -- Gallium3D just acts as a 'very thin wrapper,' allowing developers easy access to Direct3D's goodies.
Luca Barbieri, the developer behind this new code commit, has a lot to say about Direct3D versus OpenGL, which might pain some open source advocates: "Thanks to a very clean and well-though design done from scratch, the Direct3D 10/11 APIs are vastly better than OpenGL and can be supported with orders of magnitude less code and development time."
Then speaking about why Direct3D will be the graphics API of choice, when developing for Linux, Luca continued the barrage: "A mature Direct3D 10/11 implementation is intrinsically going to be faster and more reliable than an OpenGL implementation, thanks to the dramatically smaller API and the segregation of all nontrivial work to object creation that the application must perform ahead of time."
As I understand it, Wine can't yet take advantage of this new development -- but as it stands, you can now leap right in and start programming a 3D Linux application using Mesa and the Direct3D state tracker.