finding the covers of cds lying around is a good memory exercise. its like u try to remember the cd before proceeding to the rack and finding the cover. than sometimes you find another empty cover and proceed to the piles of cd thus forgotting the initial cd cover that should be looked for. this might work vice versa also when trying to remember the cover and look for the cd.
during this whole process you need a good memory to remember what you're looking for.