The new drutil utility has some nice features (see the man page). If you run
drutil bulkerase quick in a Terminal, it will start the Bulk RW Eraser. This app opens the CD tray and asks for a disk. When you insert one, it erases it, opens the tray again, and asks for another one, ad nauseam:
~ % drutil bulkerase quick
Bulk RW Eraser
Please insert erasable media in TOSHIBA DVD-ROM SD-R1312.
Erase completed.
Please insert erasable media in TOSHIBA DVD-ROM SD-R1312.
Erasing... [**************************************
....
Just push control-C when you run out of disks. Very handy when you have a big stack of them to wipe. You can also do drutil bulkerase full if you're feeling paranoid.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031114152914804