Made it in Meteor over the last semester and winter break. I use YouTube to listen to music, and found native YouTube playlists to be nearly unuseable - so I made mixtape. A simple, no-bs webapp that does exactly what you want.
You also have the ability to collaborate on your playlist, by sharing it using the link generated for you below!
Show HN: mixtape. An unintrusive collaborative playlist webapp
mixtape.meteor.com