Spotify - Map shows when two people play same song at same time
Tragofone - White-label VoIP Softphone with WebRTC and Auto-provisioning
SoundCloud - Enjoy music & follow favourite artists
PhonerLite - PhonerLite enables your PC to use it for internet telephony (VoIP , Voice over IP, SIP).
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
tSIP - tomeko.net/software: SIP client for Windows.