From Kunal Dua:
With the release of iTunes 7, album artworks are a minor rage. While Tiger ships with an album art screesaver, Panther doesn't. This screensaver is an attempt to fill the Panther void.
I have tested this with iTunes 7 and Mac OS X Panther 10.3.9, but I don't see any reason why it shouldn't work with other versions.
Note: The screensaver needs iTunes to be running. If iTunes is not running, it will be automatically started when the screensver starts.