The Music N*** is a simple replacement for iTunes, suitable for parties. It lets your guests queue up songs while locking the screen (kiosk mode) and disabling the playback controls.
The Music N*** should be able to play iTunes Music Store files (those with DRM), but I haven't tested this because I've never bought any songs from Apple. But I know it won't play over AirTunes since that's a closed feature of iTunes. There are third party ways of getting around this. The Music N*** requires at least Mac OS X 10.3 and it might not be able to read iTunes Library files before iTunes 6.
If you are like me and have no hip hop music and a guest complains, you can have him bring his CDs in from his car and import them into your iTunes library. Then you can 'Reload iTunes Library' from the 'File' menu (command-R) and the new songs will be available from within The Music N***, without the music ever having to be stopped.
Warning: As part of kiosk mode (where screen is locked), the Finder is stopped. So make sure you aren't doing any Finder operations (like copying files). When The Music N*** unlocks, the Finder is restarted. If this fails for some reason you can restart the Finder by hand by clicking on the Finder icon in the dock. Stopping the Finder is not good, however the alternatives are worse.