Many mp3 players support album art, showing it to the user in the display. Several software players support it as well, for instance the Itunes Control plugin that I wrote about earlier this week. I don't know a single application however that can process a entire music library automatically and add album art to it.
Apple's iTunes does it almost. You can select an option in iTunes to download album art of all selected songs using the iTunes store. That downloads lots of artwork, the main problem however is that this artwork is not added to the mp3 file directly but to a database only. If you use another application like Windows Media Player or XBMC the artwork will not be displayed. That's a big issue if you transfer the music to computers without iTunes.
That means that I won't be using iTunes to add album art to my mp3 collection. The best way that I discovered is to use Media Monkey. It's semi-automatic. You select all mp3s of an album, right-click the selection and select Auto Tag From Web or press CTRL + L instead.
It can take some time if you have a large collection of mp3 files but it is definitely worth it. The process does not only add album art to the mp3 collection but also tags the files properly. It takes about 10 seconds per album.
I sorted my collection by album in Media Monkey at the beginning and began to work the mp3 collection from top to bottom selecting all songs of an album each time.
Update: Media Monkey is available as a free and commercial software program for the Windows operating system. The developers have recently released version 4 of the music software.
Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.