I realize that there are a bunch of nifty automatic techniques for cleaning up your iTunes library and removing duplicate songs, but sometimes I feel like I want to do something manually (I have had some batch mishaps in my past).
Anyway, this just occurred to me as I was cleaning up my music library. If you arrange the iTunes library by song length, you can quickly scan for matching song lengths and then look for matching artists (because sometimes the title doesn't match, and hence batch processing or applescripts don't always yield proper results).
From there you just simply hit the delete key and remove the duplicate, a very simple yet effective way to clean up your library.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030211062908244