I've been asked, on a fairly regular basis, how one accesses the iTunes library of another user of the same Macintosh -- how an individual might listen to the music stored within the user account of her significant other, for example. In the past, this required a fair bit of trickery in the form of moving music collections to publicly available folders. If you have a cooperative relationship with that other user, this may no longer be necessary.
One of the more impressive developments in iTunes 4.5 is its ability to share iTunes libraries between users on the same computer. To do so, you must fire up iTunes under each user account and switch on Sharing in the iTunes Preferences window. Once you do so, other users' libraries will appear in the Source list, looking and behaving almost exactly like libraries shared across a network.
"Almost exactly?" Well, yes. The significant difference is that you can play tunes from different libraries simultaneously. Start playing a song in one account and it will continue to play when you switch users and play a different song in that other user's iTunes library.