Documentation: http://remi.github.com/Owin.Common
Screencast: http://www.viddler.com/explore/remitaylor/videos/52/
I'll be making the screencast available on http://remi.org shortly in a number of downloadable formats, so you can view a higher quality video.
I also intend on releasing more Owin screencasts in the coming days and weeks.
Owin.Common is released under the MIT license.