Jewelcase displays the album cover art for tracks in iTunes (Mac only), mocking up the look of a CD jewel case. The case can rotate if you want it to, with the track listing for the album appearing on the “rear” of the case. Jewelcase offers other features including the ability to show the artwork when the track is being streamed from another computer – something that iTunes on its own refuses to do.
To try Jewelcase, download it from Optical Alchemy. If you like it, $10 will buy you a licence.