I have a friend who shall remain nameless, but he spends a decent amount of his waking weekend hours sorting his iTunes library. His biggest pet peeve in life is a song without album artwork...
Good to know, then, that there's a free application you can download that works like a charm for sorting unruly and unorganized iTunes libraries.
Pollux, a free beta application for Mac OS X, recognizes the audio fingerprint of the tracks you've uploaded or downloaded and corrects the song's title, artist, album, art, lyrics and more.
Now personally, I've never been very careful about organizing any kind of files, so I've never seen—nor sought out—an application like this. But over at Lifehacker, where we first potted this site, they've tested it out against some other known iTunes organizers and found that, for it's price, it's one of the best out there.
Head to Pollux's site to check it out.