Meludia - Listening exercises and to sharpen your ear and music theory skills
Spotify - Map shows when two people play same song at same time
GNU Solfege - GNU Solfege is free music education software.
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
Auricula - Practice your sense of hearing and learn to identify intervals for your musical development.
SoundCloud - Enjoy music & follow favourite artists