One of the knocks on iTunes is the hoops that one has to jump through to get album art to display for your mp3 library. This is much simpler in WinAmp or Windows Media Player (WMP). In fact, it's so easy in WMP that almost my entire collection has album art. So, even though I've got all this cover art, there's no pain-free way to import it into iTunes.
Well, it doesn't have to me so hard anymore. YVG Software has a freeware app called iTunes Art Importer that will compare your library to Amazon.com and download the appropriate album art. The search is very quick and pretty easy to navigate. You can modify the search actions and approve the album art. The program looks just like iTunes – a really nice touch. You'll need iTunes for Windows 4.5 or greater and the Microsoft .Net Framework 1.1, but both downloads are available on the YVG Software site. Check it out.
Update: The fastest way to download the cover art is to just let it try to run your entire library, then manually finish up anything Amazon didn't have. Cool!!