I don't put my CDs or DVDs up after I use them typically. I tend to stack them in a pile on my desk or on the shelf behind my desk. I guess the kids learned the same thing from me since they tend to leave discs stacked as well. That means we often end up with games and movies that are too scratched to play.
Instructables has a how-to that will walk you through the steps to make your CDs and DVDs playable again by fixing the scratches with Vaseline of all things. You smear the petroleum jelly on the disc and then wipe it back off.
I remember using that stuff on my kids' diaper rash when they were infants; it is hard to get off just about any surface. The instructions suggest cotton balls, alcohol, and elbow grease for removal. Even severely scratched CDs are said to be repairable with this method.