The CUDA library provides a direct, general purpose C-like SPMD programming model for NVIDIA graphics cards (G8x series onwards). This is a collection of bindings to allow you to call and control, although not write, such functions from Haskell land. You will need to install the CUDA driver and developer toolkit (tested with v2.3).

http://developer.nvidia.com/object/cuda.html

Note that on Snow Leopard, the c2hs preprocessor is confused by the notation for Apple's Blocks extension, so to work around this:

cabal install --c2hs-option=-ccpp-4.0