These take pre-created playlists and evenly shuffle them together into a new playlist. You can make a "battle of the bands" playlist, alternating between bands. You can shuffle 5 genres (for example, Jazz-Country-Rock-Folk-Metal) so that every 5th tune is a jazz tune. Perhaps you'd like to alternate between new tunes and old tunes, your wife's favorites and your favorites, etc. These scripts make this easy to do.
(Note: In order to launch this PowerPC-era script on an Intel machine, it must first be opened and then saved using AppleScript Editor, which is located in your /Applications/Utilities/ folder. More information is here.)
Exports and then re-imports selected tracks' artwork
Set new Last Played/Last Skipped of selected tracks
Create a PDF booklet containing info from the selected tracks
Renumber order of selected tracks
Update subscriptions which have expired by virtue of being ignored for five or more days
Remove iTunes tracks disassociated from files