I'm a real fan of Smart Playlists in iTunes 3, and have been finding some interesting uses for them. For example, you can make a Smart Playlist that will show the history of whatever tracks you've played back in iTunes. This can help you find a track you listened to a while ago, but can't remember what it was -- helpful if you try out random tracks from a large iTunes Library.
Of course, iTunes keeps track of which songs you've played, so even if you have a random playlist, you can just use the forward/back track commands to go through your recent history. Having a History Smart Playlist has the benefit of showing a list in the main iTunes window. Here's how to create one:
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