Plug - Lightweight OSX player for Hype Machine
Spotify - Map shows when two people play same song at same time
Magic Playlist - Get the playlist of your dreams based on a song
Muru Music - Personalised playlists within seconds.
Playlist Hunt - Playlist Hunt is one of the best applications for Apple users to get the best music through it.
Vinyls - Vinyls is a music player that lets you listen to your music without any complicated setup.