Artworker makes iTunes download all your album art, so you see no more "Artwork could not be found" messages. It does this by passing information from your copy of iTunes to a search engine, via the Artworker server (you'll need to enter your Admin password to authorise this). You'll also need to turn off Web Sharing, or any other service using Port 80.
Version 1.0: Initial release.
Mac OS X 10.6 or later