Vialogues is a free service that allows you to build online discussions around videos hosted online and videos that you have saved on your computer.
Registered users can upload videos to Vialogues or use YouTube videos as the centerpieces of their conversations. After you have selected a video from YouTube or uploaded a video of your own, you can post poll questions and add comments that are tied to points in the video. Your Vialogue can be made public or private. Public Vialogue's can be embedded into your blog or website. Embedded below you will see a Vialogue that I started around John Green's video about the Vikings.
Applications for Education
Vialogues could be a great tool to use to publish questions for your students to answer while they are watching a video that you have created or found online. You could also use the comments in Vialogues to simply call attention to a specific point made in a video. I'm thinking that I would write comments like, "make sure you know this when you write your essay."