I had an old Western Digital external hard drive lying around, & the superdrive on my macbook pro is bust, so I ripped the old case open & took out the board that has USB, power & SATA, & plugged in a DVD drive where the hard drive would have been. It powers up & all, just snow leopard won't recognise it as a superdrive, in system profiler it shows up as an external hard drive.

EDIT: A fix for the superdrive, at first it was spitting out almost every DVD or CD I inserted without mounting, reading the odd one, I was about to give up & buy a new one when I decided taking the superdrive apart & cleaning the laser by hand couldn't hurt, so I did, & it works great!