In reply to Submit to Gravity:
Yep, as above, give the hard drive a bit of a shuggle and there's a good chance it will wake up. Modern drives park the heads if they detect a fall so the software /should/ be safe...
If it doesn't wake up happy, then the disk may have been damaged after all. Try a boot disk and possibly kick yourself for not backing everything up.
If the drive is dead, it's pretty trivial and not that costly to replace it.