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.
Delete characters from the beginning or ending of selected tracks' name, artist, album, comments, composer, or show tags
Change file type to make selected AACs bookmarkable
Applet assists with swapping, copying, appending data between track tags
Perform search-and-replace on text in your choice of tags
Change video kind and video related tags of selected video tracks
Remove iTunes tracks disassociated from files