From Wired How-To Wiki
Sometimes pulling out an old CD from your music archive reveals some discs haven't fared well in the passage of time. CDs are vulnerable to fingerprint smudges, a bit of dried syrup from the time you spilled that Coke in the car, perhaps even some scratches from the time that CD disappeared under the passenger's seat three years ago.
If you've got some CDs that are well past their prime (and no, we don't mean that perfectly unblemished Spice Girls disc you've been hiding from your friends), fear not. There are ways to get that disc spinning again so you can transfer the music or data to a more respectable media, like MP3s.
The first thing to try with your potentially damaged CDs is a PC. Many times a CD that's too mangled to work in a car stereo will work just fine in your (much faster) computer CD/DVD drive. In addition, CD/DVD computer hardware and ROM software error-recovery differs by brand; a high-quality player will play discs which freeze or skip on a lower-quality one.
This article is a wiki. If you still buy CDs and want to help people restore their music collection, hop on and improve this article.