BatchDMG is a handy utility for times when you have to image large collections of disks (like installation media etc). Just run it (as root, to avoid an authentication dialog) and start feeding your machine with media.
The imaging starts automatically when a volume is mounted. Should also work with multiple DVD drives. The images are bzip compressed (UDBZ, need 10.4 or later to open) and are named after the volume name. It ejects the media once the imaging has completed.
Should work with 10.5 or later (uses PyObjC).