Abdul Bezrati has developed two demos for benchmarking purposes. The first demo implements omni-directional shadow mapping on hardware that supports Pixel Shaders 2.0 and float pixel buffers. The second demo generates shadow volumes on the GPU via special meshes made of degenerated quads inserted at every occluder edge. It takes advantage of Nvidia two side stencil buffer and ATI separate stencil to write the shadows in one pass. See this thread for details.