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.
Enter text for the selected tracks' Description tag
Apply selected CD's CD Text to its disc and track tags
Locates pairs of track entries pointing to the same file
Change file type to make selected AACs bookmarkable
Re-associate batch of dead tracks with files from selected folder
Displays files in iTunes Media folder not in iTunes track library