This script will allow you to merge the track contents of two or more playlists or delete any number of playlists at once, including Smart, Genius, and Playlist Folder playlists. The merge feature will prevent the same tracks that may appear in different source playlists from being duplicated and has an option to delete original playlists. The delete feature only deletes the playlist; tracks, of course, remain in the library.
Very handy when assigned a keyboard shortcut.
Also see Delete Empty Playlists.
OS X 10.6 or later only. Previous universal version (without the merge feature) available at the link below in the "Info" section.
About to merge two selected playlists to a single existing playlist. The tracks in the two selected playlists will be copied to the target playlist.
Search YouTube using tag info from selected or playing track
Remove iTunes tracks disassociated from files
Apply selected CD's CD Text to its disc and track tags
Play through each track in a playlist at your set interval
Update subscriptions which have expired by virtue of being ignored for five or more days
App displays files in iTunes Media folder which are not in iTunes library