Mobster is a companion application for iTunes that allows you to create playlists based on personalized music recommendations. It watches the music you play in iTunes and uses recommendation information from Musicmobs to suggest other bands that you may like. You can use Mobster to control iTunes, make playlists, find new music, and browse your library more efficiently.
A playcast is a podcast that you create out of a playlist. Using Playcaster and built in features of OS X, you can share your playlists with friends. Playcaster combines all of the songs from an iTunes playlist into one large MP3, then uses OS X Web sharing to build a podcast out of your playcasted playlists. Your friends can subscribe to your feed in any RSS reader or iTunes and listen to your playlists.