Last night, I tried to play a DVD in my Macbook Pro; the movie stalled and then DVD Player quit entirely. When I checked the disc, I found it was scratched.
I discovered that I could still watch the film by ripping the DVD to my hard disk with MacTheRipper, and then viewing the ripped version. I presume the error correction routines are more robust in MTR than they are in DVD Player, and so MTR is better able to scavenge data from scratched disks.
Even better, I was able to start watching the movie before the rip had completed!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061211124747388