Spotify - Map shows when two people play same song at same time
Knowthelist - Knowthelist - the awesome party music player Easy to use for all party guests
Deezer - Deezer is a music streaming app created in France. It is available in 180 counties and gets 16 million users a month. 6 million of the users have paid subscriptions. Read more about Deezer.
Song Director - Song Director is a program that plays and keeps track of all your music files.
Last.fm - The world's largest online music service. Listen online, find out more about your favourite artists, and get music recommendations, only at Last.fm
MixTape - Home of MixTape, an OSX application for creating beat matched mixes with simple export to the web or iTunes.