In response to last week's Best of 2007 Smart Playlist, the Podophile weblog suggests another useful iTunes Smart Playlsit: the Lost Music playlist.
If you're a compulsive music collector like me, or suffer from an advanced case of M.A.D.D. (music attention deficit disorder) there are probably a lot of tracks in iTunes that you never got around to listening to. [...]Just set up a smart playlist of all music added in 2007 with a play count of 0. If you religiously listen to every new song at least once, you may need adjust the play count to 1, just to flesh out your playlist a bit.
Not only is the Lost Music Smart Playlist is a great way to keep up with those undiscovered gems in your iTunes library, but you could also use a similar playlist (maybe throw a skip count rule into the mix) to prune your iTunes library of music you haven't lost but you just don't listen to.