http://ispc.github.com/
http://ispc.github.com/example.html
What a horrible name. It was called Volta internally. It is open source. I rather like it. It looks almost, but not quite, entirely just like C++ and is sufficiently C++ that you can write ISPC in your favorite development environment with your favorite libraries and it'll probably work just fine. It vectorizes loops. Compare and contrast with C++ AMP (coming later).