Good write-up on how to setup your Raspberry Pi to mine for bitcoins. But….is it worth it? The CPU cycles the RPi has are pretty low so you would need a bunch of these to even come close to the mining rigs out there. Only thing I could think of is it could be a good use of the system when not doing something else.
http://www.instructables.com/id/Bitcoin-Mining-using-Raspberry-Pi/