I'm kind of late to this party...however an alternative to Keith's site is Amazon. They have all of his stuff, and I mean all. I was able to source his old VHS tape there. It's where I've gone for my Twist goodies. Okay one time at bike camp, I mean when I was showing my sister around SF, we went to Green Apple books. They had some Twists books there (I think one was even signed--I should have kept that one!) and I got the books for my sis.
This
search link should get you most of his stuff. Be ready to order more because the running gag in the video about how you "lend" the book to a buddy and it never comes back is true--either that, or you end up buying them one too.
Great books/videos and a huge thanks to Keith for all his effort.
I do have one question about the books for Keith--is there a way to get, or have you put the books out so that we can have them on our iPads? Apple has some amazing iBook publishing tools (that are free) where you could put Twist on an iPad, and even include some video and animation. The tools are easy to use, and it sure would be a pleasure to have the Twist content on that platform too.