I found a Sherlock utility for grabbing album cover art from Amazon. I kind of wish it was more simple but here goes. Using First River, find the album you want, click on Tracks in the tabs at the bottom of the window, and at the bottom of the song list is the large version of the cover art. I have copied and pasted the artwork, and dragged and dropped it into iTunes -- both work. Cheers to hints.
[robg adds: With the slow-but-sure fading away of Watson, I've started to use Sherlock more often. Watson was my favorite tool, but its purchase by Sun seems to have done nothing more than insure its disappearance from the face of the planet (no progress update of any sort since October of 2004?). Sherlock isn't Watson, but it's not all bad, either. And this Amazon plug-in is amazingly useful, for much more than music. I'm now using it to do most of my Amazon searching; it's faster, easier, and the results are very nicely organized. One caveat -- though it's free, the developers do attach their Amazon associates tag if you click a link from the plug-in to the site -- so that's how they get paid for its use.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050310143412616