I know for OS X there's a program called Acquisition that is pretty good. However, if you're in 9 (and only looking for MP3's) I would recommend AudioGalaxy. Go to
VersionTracker, search for "Mac Satellite" and download the latest version. Open that program, start a new account in preferences and then go to
AudioGalaxy (in your web browser) and search for the MP3's that you want. You can then queue those through the browser and it will download them through Mac Satellite once they are ready. Again, this is only for MP3's, but you can find almost anything.
Also, of course, someone already suggested this, but I love Carracho. It works great and it's relatively easy to find servers. If you need servers/trackers, go to
tracker-tracker . Anyway, good luck and happy downloading!
-ArtMan617