The collection of valuable YouTube videos is growing at a tremendous pace. Please take the time to preview some of these sites: 100 Best YouTube Videos for Teachers and YouTube Education: 80 Intelligent Video Collections. Many universities, such as MIT, are placing significant content on YouTube through the OpenCourseware initiative. Many of these sites are also easily accessed through iTunes U. It doesn't end there. The House and Senate have YouTube sites. And, believe it or not, even the Pope has a channel!
But wait there is more. I realize that YouTube may not be available for all, so here is a link to 20+ educational alternatives to YouTube. One more bit of advice, some featured videos and comments that appear alongside videos, may not be appropriate for the classroom. To limit that exposure, here is a video that shows you how to embed a YouTube video into a PowerPoint.