BURN-Proof stands for buffer underrun proof. A buffer underrun is when the drive feeding data to your CDRW can't keep up and the buffer on your CDRW, which holds the data that is going to be burned, empties out. The CDRW then has no data to burn and it gives you a buffer underrun error which results in you having to toss the CD and start over. With a BURN-Proof drive, your CDRW will remember where it is in the burn process should the buffer ever empty out and then start from that point when the buffer fills back up again.
The consensus around here seems to be to go with Plextor drives. A lot of people like the TDK drives as well; I have one myself, but both of those are probably out of your price range. Take a look at the 12x10x32 Lite-On drive for $95 at newegg.com. Many people like these drives because they are inexpensive and have BURN-Proof technology. You can get the 16x10x40 version for $20 more. It's up to you to decide whether it is worth it or not. With a 16x you're really only shaving about a minute and a half off of burning time when compared to a 12x.