TuneSleeve is a utility that downloads album art from Amazon for each album in your iTunes library (or in a specific playlist). You can choose which image is the best among all the images returned, and if there is no good match you can launch a search on Google Images in you browser then drag&drop the desired image on the album in TuneSleeve.
||Free to try
Windows Server 2008
||Microsoft .NET Framework 3.5 SP1, Apple iTunes