Spotify - Map shows when two people play same song at same time
YoutubeMultiDownloader - Just like its name YouTube Multi Downloader, it is an online website for downloading the videos of downloading without using any video download and accelerator.
SoundCloud - Enjoy music & follow favourite artists
KeepVid - A free web application that allows you to download videos
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
ShareTube - Watch YouTube, synced with friends.