I have my iTunes library on my Mac mini with an attached RAID and the big stereo attached.
When I am now working on my Macbook, I still want to hear music without always going into the server room to operate iTunes.
This is one of the reasons why I wrote the little AppleScript described in another posting.
But this solution as nice it is, is not the best. Some searching around led me to
iTrc is a little desktop app that lets you remote control another iTunes instance. You can select the various playlists you have, search your library and have the results playing as a new playlist, jump to next and previous songs and also rate the currently playing song.
iTRC is published under the BSD license and available as source and binary.
Very nice little app!