I'm not sure if this has been suggested yet - but try waxing the bottom of your cd's with car wax :-) go through the whole process - wash them with a mild, warm soap solution and a VERY SOFT cloth, NOT terry cloth - try a cloth baby diaper or the inside of a sock (for christ's sake, use this for your car too). Then use a separate clean, dry super-soft cloth to apply the wax, apply in small circles, using very little pressure. Finally, use a 3rd clean + dry super soft cloth to buff the surface - I generally wipe from the center of the CD to the outside Edge (in the case that the buffing process causes any fine scratches,- those that are perpendicular to the CD "grooves" cause little or no distortion). I've done this on dozens of CD's to get my songs onto my Ipod - and it's worked great! I'd say this method will fix 80% - 90% of scratches. It won't fix the huge ones, but it's better than nothing
