CD Art Display is a skinnable gadget that appears on your desktop and shows the CD cover of the currently playing song. It reads cover from player’s database, local folder or ID3v2 tag and can also search for covers online if they are not found locally. The software offers a slick interface with transparency and alpha shading and playback controls to pause or skip to the next track in the playlist. Other features include lyrics display, lyrics editing, cover display in tray icon and more. CD Art Display currently supports AlbumPlayer, Helium Music Manager, iTunes, Winamp, Windows Media Player, MediaMonkey and partially supports foobar2000 (with Winamp API Emulator plugin), MP3Toys, qmp and musikCube.
CD Art Display is a freeware.
Download CD Art Display here
Download skins for CD Art Display here
iHacking 
The program is very funny, but with the mp3 untagged or tagged in the bad way, the image recognizer doesn’t work fine…
Good if you have a small number of albums.