reEmbed - Custom YouTube Video Player
Spotify - Map shows when two people play same song at same time
TabFloater - Browser extension to use picture-in-picture with any website
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
Vid Repeat - Loop YouTube videos for X minutes or for X times. Loop a full video, or only a selected part, add a delay between the loops, and share the loop with your friends.
SoundCloud - Enjoy music & follow favourite artists