I can't count how many scratched CDs I got laying around that I don't know the content inside them, but this might be a good start to revive them. Also, in the past I tried to use other products and techniques that didn't solve the problem so this might be it.

Instructables has published a quick and easy way to remove the scratches from the CDs. It worked with them, and I hope it works with me too.

A can of Brasso Metal Polish and a paper towel (or a cotton cloth like a user commented) is what you need, then, pretend to be karate Kid in the movie when he is polishing the car... just replace the car with a CD.

Via instructables