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!
Author here! I listen to a lot of music on YouTube, and found the native YouTube playlists next to useless, so I wound up making this clean and collaborative playlist webapp to solve this problem, and of course to get my hands dirty with Meteor!