Discovery Education, best known for it's Streaming video service and Science TechBooks, also has a great YouTube Channel. Discovery Education's YouTube channel has great resources, including webinars for teachers, and many other videos. They have playlists and tags so that you can better find what you are looking for.
The webinars are excellent, with many of them from Steve Dembo, on all kinds of topics including Web 2.0, Social Media, how to use Discovery Education products and resources, and much more.
Check it out!
Great Resources from Discovery Education
Discovery Educator Network - great resources and great addition to any PLN