I have a cd wallet I intend to start filling and have thought about this a bit too. Am thinking of getting cd labels to print using the computer and colour code them according to what key they are in, then roughly keep the same genre on each disc and just label the date I burnt them. Eg. songs in keys 1 and 2 go on a disc with a blue strip on them, labelled 19/2/12 electro I'm contemplating doing it like that, but would be interested to see how everyone else does it