Extremetech takes a look at the present and future of GPGPU:
The first hint of graphics cards doing something "more than 3D" was with the introduction of video acceleration. It started out simple, with partial decoding of MPEG video, moving gradually into full acceleration of the MPEG2 used in DVDs, and today is quite robust. Modern graphics cards accelerate much of the decoding steps required for sophisticated codecs like VC-1 and H.264 (both used in Blu-ray movies), along with de-interlacing, noise reduction, dynamic contrast control, and more. Much of this work is done in dedicated video hardware on the GPU.
The release of DirectX 10, with unified vertex/pixel/geometry shaders and stream-out functions brought with it a class of hardware that is more flexible, and more easily able to handle other computing tasks. Research into using the powerful parallel processing of GPUs has been going on for years. They call it "GP-GPU," for general-purpose computing on a GPU, and it's about ready for the mainstream.