One thing that works good for cd's is facial oil. I know it sounds gross, but grab a scratched cd and rub it against your forehead, get it good and oily, then proceed to polish the cd, and it works pretty ok, it's not the best. But, your own body produces it, it's more than a household item you have around, and facial oil when polishing with it makes **** look great too.
Of course if you want to go the extreme way of retrieving cd's enough to back them up and re-burn the image. I take a dull pairing knife and i buff the scratches out manually enough to make the cd drive be able to read the whole cd slowly, but enough to make an image of it on my hard drive. My friend came up with a more efficient method where you have a portable disc player and you keep the lid open and put the disc on upside down. The disk will spin while you take a toothbrush and just go all along the whole cd which results in buffing the whole cd just enough so you can backup the disc and re-burn it later. Or of course load up the image in a virtual drive. I prefer to do it manually with a pairing knife isolating and buffing only the scratched areas that i see, as opposed to buffing the whole cd. And of course this is without using facial oil and polishing the underside of a cd with it.
Of course i'm an extreme mofo, but doing it this way, you save money on buying a disc doctor which works no where near as good as me doing it. Like i said dull pairing knife, or if you're a beginner and don't want to it manually, do the upside down cd player toothbrush method and buff the whole cd. Of course to get rid of a scratch with a dull pairing knife point just sort of massage the scratch out of the cd(cd plastic is pretty malleable) until all you see is like some slight ripples in the cd plastic which the laser on the cd drive is able to work with as opposed to full blown scratches.
More on facial oil...
I once took my friends lord of the rings sword that the humans used in the movie, and rubbed my face and forehead all across it when he was out of his dorm. And then i polished it, it looked absolutely great, better than ever. When my friend saw it when he came back in he was impressed. When i told him what the **** i did to his sword, he said that's gross and don't do it again, but he liked how good it looked. Anyway go whatever way you like when recovering a cd, i like using human ingenuity, and that's what the dude in the link posted who used hair gel did. It's just i don't have hair gel, i don't have to purchase any oil, and a dull pairing knife point works great...among a toothbrush(my mom always yelled at me for using her pairing knife for cutting wire of any thickness...it's what made the knife dull enough for cd's, and i guess still good enough to cut veggies