Discovery Education is a great resource for teachers. I recommend it to my colleagues often and suggest that they create a free account on the Discovery Educator's Network (DEN). DEN has a lot of great free resources available, including uploaded resources from other educators. You can also apply to become a STAR Discovery Educator and become elligible for more resources.
They have videos, lesson plans, games, and more.
This is the same company that brings you Discovery Channel, Discovery Streaming (formerly United Streaming), TLC, and more.
If you already have a Discovery Streaming account, you can use that to sign in to DEN.
Go to the site and explore a bit. It is well worth the time.