Explania is a very cool site I learned about recently. It was created by a multimedia company, Instruxion, and includes animated explanations, interactive tutorials, and instructional videos. All of these can also be embedded into other websites.
The materials are organized by channels and by subject and organizations can have their own custom activities made and their own channel.
It is free to use and access, and there are some really good materials on the site that teachers can use in their lessons or as help for students.
