Album Art Downloader is a freeware which lets you download album art for any artist music album in the world, It looks for so many places to get the album art that you can easily get all the album art covers for all the music on your computer.
Here a small screen shot of the program while it is searching for album art
[ click the image above to see in full size ]
It lets you download album art from so many places which includes album art exchange, amazon, buy.com and so many other sources from where it can get the album art based on the artist name or the album name.
You just need to click the floppy save icon on any of the album art to save to your computer instantly without any issues and place it in the music album folder.