Rubbing Vaseline on scratched CDs to make them readable again is a new one to me, but Instructables has a DIY project up claiming it works perfectly. Mind you, they also say peanut butter works a charm too.

Using a piece of cloth, the Vaseline can be slicked onto the scratched CD, and then rubbed off with some rubbing alcohol on a cotton ball, leaving the Vaseline in the scratches, filling them in. It won’t remove the scratches completely—that would be a miracle—but it sounds like it does a nice job of filling them in to make the disc work again.