Clyp - Clyp is the easiest way to record, upload and share audio. No account required.
Spotify - Map shows when two people play same song at same time
Audio Hijack - Record any audio, with Audio Hijack!
SoundCloud - Enjoy music & follow favourite artists
Loopback by RogueAmoeba - Get all the power of a high-end studio mixing board, right inside your Mac!
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