If you're a teacher you must check out TeacherTube. The site went live just a couple of weeks ago on March 6, 2007. Think YouTube but for education. Pretty slick interface and easy to use. Teachers are currently uploading video relating to education. Yesterday I wanted to try it out so I upload my Constitution Day video from this year - we do a video each year and show it on our building student broadcast to celebrate Constitution Day. Just like YouTube, it is easy to upload video content, easy to embed in your blog, easy to send a link and collect your favorite videos.
If you haven't yet checked out TeacherTube go over and check it out.