3D First Person

Does anyone have any good references/sources for building a 3D first person game?  I'm looking for multi-platform, so preferably not DirectX.  And I'd prefer C++, but it could also be C#, or Haskell.  Any help appreciated,

opengl, linear algebra, and vector operations should be good. Add sockets if you want multiplayer. C++ will be sufficient but you are welcome to experiment with others. Just make sure you can keep up a decent framerate is all.

I'd recommend writing a software renderer for real mode 386. Check out Chris Hecker's guide on texture mapping.

Just use an existing three 3D dimensional engine.  Your game will likely be fast, and there will be some chance that you will actually release an alpha.

Use Ogre3D or create your own assets for the Sauerbraten engine.

lrn2lisp

Irrlicht.

pANDA3D