Ask HN: Resources for learning general-purpose GPU programming?

I'd like to learn how to program for GPUs using either CUDA or OpenCL, and was wondering if anyone here could recommend a resource that could help me get started.

It would be awesome if there were a book or tutorial that walks you through environment configuration, and then shows you some examples of how to use the GPU to solve some real world, non graphics problems.

For the record, I'm not asking about graphics programming or OpenGL, I'm asking specifically about general purpose computing on GPUs.