Well, would you like to have the ability to simply right click on your Nautilus file manager and get the official album cover without having to open the audio player???... in that case CoverChooser is a must have. Other than that, since it's a standalone application, you can use it without the help of Nautilus as well. At this moment is support fetching covers from online source such as ...
*. Amazon (for that you'll need a personal "key", more later).
So basically... the possibility of you not getting the cover of your favorite audio album is kept at minimum :P. You can install CoverChooser in Ubuntu (11.04, 10.10 to 9.10) by entering the below command in Terminal.
sudo add-apt-repository ppa:panthora/coverchooser-ppaIf everything went smoothly, you should be able to access it via : Applications -> Accessories -> CoverChooser.
sudo apt-get update
sudo apt-get install coverchooser
And as said before, if you want integrate it with Amazon's web-service, you'll need to get a personal key which you can get it from here (don't worry, it's free).