A neat little proof-of-concept/research project from Toshiya Hachisuka is the “Parthenon” rendering, a GPU-accelerated global-illumation renderer. It boasts a nice collection of features like direct illumination, indirect illumination, and a hybrid approach of both CPU and GPU algorithms.
His website contains PDF’s of his presentations on the work from SIGGRAPH presentations and his GPU Gems 2 contribution, as well as the EXE for you to download and play with. Requires DirectX9 or later, and a video card that supports floating-point buffers, vertex shader 2.0, and Pixel Shader 2.0
