There appear to be 17 of these. I have listened to them all, but most of them a long time ago.
I'd be interested in this archive if somebody put it together.
I'll get you started real quick:
October 15, 2013: Fill-in for Tom Scharpling
June 18, 2013: Mike discovers Ke$ha. Therese puts the kibosh on the Depravity's Rainbow van plan.
May 7, 2013
March 26, 2013
December 11, 2012
August 21, 2012
May 8, 2012
January 24, 2012: State of the Rainbow
October 18, 2011 (note: archive is on the main Best Show site)
February 1, 2011: Talking cruises w/ John Hodgman and Depravity's Got Talent!
June 29, 2010: Fill In For Tom Scharpling
April 27, 2010: fill-in for Tom Sharpling
April 6, 2010: Fill-in for Tom Sharpling
February 16, 2010: Fill In For Tom Scharpling
December 30, 2009: Fill-in for Seven Second Delay
October 20, 2009: Fill In For Tom Scharpling
October 13, 2009: Fill In For Tom Scharpling