YouTube have a beta tool - annotations. I'm sure more features will appear soon as YouTube have acquired Omnisio
but this will have huge implications in any curriculum area where the creation of media is core. I teach music and I've been waiting for something like this for a long time!
I've done a trial of how a music track might be delivered in YouTube with an ongoing analysis. Currently it is not possible to include the annotations when the video is embedded outside YouTube, so I'll just link to the original page