This script uses the UNIX qlmanage command to display a Quick Look window of the selected track(s), which can be audio, video, and, perhaps most usefully, PDF, whereby Preview.app is not necessary. Also handy for playing a single track out of playlist context. Need I add that a keyboard shortcut makes this very handy.
Caveats: 1) under Leopard a media file will begin playing immediately, so the script uses a hack to prevent this, 2) under Snow Leopard and better the QL window's title contains "[DEBUG]" which cannot be suppressed, and 3) the QL window can only be dismissed by clicking on its close box.
Copy chosen tag info from one set of tracks to a different set of tracks
Displays files in iTunes Media folder not in iTunes track library
Set the Plays of selected tracks.
Apply selected CD's CD Text to its disc and track tags
Search for lyric sites with Google using info from the current or selected track
Remove iTunes tracks disassociated from files