Discovery Education has a lot of great resources for educators, many free (over 30). They also have fee-based services such as DE Streaming with thousands of videos, audio files, images, lesson plans, and much more.
One of their other resources that I have been using lately is the Discovery Education Science Techbook. It is more than a digital textbook. "It’s a different way of thinking. Thinking outside the box, perhaps. Or more appropriately, thinking outside the book."
Trial Request: Please contact Discovery Education representative Brett Jacquay, Education Manager, firstname.lastname@example.org