ParticipateDB

From the about page : Vialogues (which derives from “video dialogues”) is an award-winning discussion platform that proves that videos are both powerful teaching resources and the ultimate conversation starters. Vialogues provides a space for users to hold meaningful and dynamic time-stamped discussions about videos. Vialogues is being developed by EdLab , a research, design, and development unit at Teachers College, Columbia University.