We all know about You Yube. Some of us may use TeacherTube.
Next Vista for Learning also has videos, its focus is a bit different. "Its central project is a free, online library of teacher- and student-made short videos for learners everywhere. Next Vista believes a strong four-minute video could save students days or weeks of frustration by providing a variety of presentations on the topics that give them trouble." There are three categories of videos: Light Bulbs are instruction on various topics, Global Views are made for and by teenagers with intros to different parts of the world, and Seeing Service contains profiles of people "who make life better for others". This site is young and I believe the founder, Rushton Hurley, is looking for contributions.