Just like I was expecting, IBM releases an OpenCL drivers for the Cell but actually also for the POWER6. There is a SDK, a forum and review system, it looks quite serious to me. I'm not a specialist in IBM chips so I can't say either or not the PS3 Cell is supported, I wish it is!
All major desktop actors have release something for OpenCL: Apple, nVidia, AMD and now IBM... All? Not really, Intel is missing... It is actually possible to use the AMD OpenCL SDK on Intel CPUs. Intel is doing great CPUs chips and it is mostly it.