How can videos help us deepen inquiry into teaching math, and student inquiry into learning math?

I’m slowly finding videos of math teaching and learning on the web, and trying to compile them here. One of these days I may have to graduate from one list into categories, but for now, they’re in the order I discovered them (oldest at the bottom):

And, from my twitter-friend Chuck Poole, a simple Google Doc his students use to assess their own groupwork: The students watch the video of their group working and self-assess.