I've actually got a script that I've made for doing that. I've been cleaning it up somewhat recently for doing a proper release. It lets you schedule things based off of any ICAL based calendar along with just a set of default playlists.

It's probably a little more obtuse and annoying than just the party mix thing in iTunes since I originally designed it for running a jukebox/micro FM station.

https://github.com/simcop2387/MediaSched