I accidentally pulled my external enclosure off my desk thanks to the incredibly long 1 foot USB cable. Now my WD 200 GB Caviar drive beeps twice at me, waits 5 seconds, then beeps twice again, and just keeps going. I assume this is a bad thing, but does anyone know what it means? It ran perfectly until this happened.
Thanks.
It means you damaged the drive and it is most likely about to fail.
Your drive may have a seized spindle motor, or a stiction fault. Stiction occurs when the heads land on a smooth section of the platters instead of their normal landing zone.
See http://en.wikipedia.org/wiki/Stiction#Hard_disk_drives
Stiction forces can often be overcome with gentle “percussive maintenance”. 
This thread may interest you (it has a couple of success stories):
http://forum.hddguru.com/samsung-portable-500gb-dead-t14351.html#p99445
See the warnings on page 5 of the following article.
Disk Drive Science (Steve Legg):
http://eprints.soton.ac.uk/7803/5/DiskDriveScience_copy.pdf
Here are photos of what can happen:
http://forum.hddguru.com/viewtopic.php?f=1&t=15911#p105001
