YOUTUBE DISCO :
we already knew that we can play our favorite musics in youtube but may be you didn't know that you can use youtube as a disco, you can search, mix, create playlist and play. Youtube DISCO automatically puts together a playlist of songs from your preferred genre or artist.
Go to http://www.youtube.com/disco and enter any artist, song, or genre and youtube will populate a playlist of the most watched/ popular videos from your search.
You can also set it to play the current top hits and it will tell what videos are most popular at the moment.