Check out ATI’s Ashli Demo . It’s basically an effects viewer type of program that contains a bunch of RenderMan shaders that get rendered in realtime. It can compile the RenderMan shaders into DirectX 9’s PS2.0 and OpenGL’s ARB_fragment_program.
Being an ATI demo, it is obviously was built for the R3xx series of video cards, though. I have no idea on what the results (quality or speed) of running it on GeforceFXs would be. . .