I recently discovered you can use the pins on the Raspberry Pi to programmatically toggle switches! As a software guy, I find that magical. I ordered a cheap 8-relay board [1], and I'll hook some stuff up to it and turn my house devices on and off via the internet!
Not to burst your bubble, but Raspberry Pi IO pins operate at 3.3 volts, and the board you linked requires 5 volt logic inputs. It might still work, since there are no specs available for the transistor on the board, but don't count on it!
The Raspberry Pi provides a 5V out pin at ~ 300 mA, so it should work, if the transistor works at 3.3V. Also, someone has tried it, and it worked. I just hope it's the same board.
See http://wiki.creativecommons.org/4.0/NonCommercial especially "NC Proposal No. 9: Create a new CC license, NC-EDU, that prohibits non-commercial uses, but allows educational uses" for further discussion of this issue.
