I picked up a Seagate Barracuda 200GB drive for $75 shipped on Amazon a few weeks ago. Check out the third party sellers, they usually have really good deals. On eBay them seem to all go for about $85-90 used.
I've got a 1gHz DP QS with a 120 and 200 GB Barracuda drives, and they're great.
ST3200822A-RK 200 is the model # I went for (it's not advertised as a Barracuda drive, but on the drive itself it's labeled as a 7200.7 rpm Barracuda drive).