Special Broadcast Tuesday, January 15th, 2008 - KPFA.org
"KPFA broadcast of the Green Party presidential debate, featuring Ralph Nader, Cynthia McKinney, Jared Ball, Kent Mesplay, Kat Swift, and Jesse Johnson and moderated by Cindy Sheehan and Matt Gonzalez. With hosts Larry Bensky and Aimee Allison, and your phone calls."
Also video clips of the debate are available via YouTube courtesy of Mike Feinstein's efforts. It's my understanding that Nader was not on the debate panel as he's not officially a candidate for the Green Party presidential slot. That being said, supporters within the Green Party of California wanted him to be able to speak and he got a more than fair amount of time as a result, imo.
Green Presidential Debate - Mirkarimi, Allison, McLaughlin - Introduction
Green Presidential Debate - San Francisco 1/13/08 - Hour One
Green Presidential Debate - San Francisco 1/13/08 - Hour Two
Green Presidential Debate - Ralph Nader - Closing
Google News reports on this event.