K12 Textbooks
On-Line Physics Textbooks - The Light & Matter Series
Dr. Ben Crowell teaches physics and astronomy at Fullerton College in Southern California. He has published a series of physics textbooks under the Creative Commons License.
Wikiverstiy - Wikibooks
Wikiversity is making great progress on creating textbooks published under an open/free license.
They already have a good start on content and a solid community of authors and lots of support. I also like the way Wikiversity fits in with the rest of the Wiki community.
The question we need to discuss is how to work with the Wiki projects. As a teacher, I have in my mind the type of resources I need for a course and it's not what I'm seeing on Wikiversity. What I see there is designed more for an individual learner, not a teacher gathering materials for a course.
Here's a short list of what I would consider as necessary in a K12EdCom based course: