HLSL? ARB? Cg? GLSL?
GLSL. There was a poll of the community - you can take a look back in the forums.
I take it GLSL is atad new
to be messing with for somthing in the next few weeks?
GLSL is on the way. I already made some tests with it, and now it is a question of nice and clear parameter separation, especially for array parameters. But, to be realistic, don't expect it earlier than in 2-3 weeks.
HLSL is for DirectX so thats out?
Yes. I do not know any HLSL implementation for OpenGL.
Cg only runs on nVidia cards- or am i wrong there?
Sould be working everywhere where ARB_<type>_program supported, but in practice, on the ATI there are some pbs.