Astro Pi

Using the GPU

https://www.raspberrypi.org/blog/a-birthday-present-from-broadcom/

i missed this – broadcom have released the specs to the graphics chips on the pi.

This allows people to do fast, fast fourier transforms on the pi:

https://www.raspberrypi.org/blog/accelerating-fourier-transforms-using-the-gpu/

And it can also be used to do SHA-256:

https://rpiplayground.wordpress.com/2014/05/03/hacking-the-gpu-for-fun-and-profit-pt-1/