If the drive itself is broke you will most likely need to mail it off to a recovery center. The prices usually start around $600 and go up quickly. I've known people who used http://www.diskdoctors.com/
but have never used them myself. If you google there are lots of places that come up. If it's just the enclosure that is broken you should be able to take that apart yourself and try hooking the drive up using a new enclosure or just directly to your system.