Daily Kos dude Markos Moulitsas Zuniga cruised through the Colbert Report last week. (April 6, 2006, I think)
Video-Markos Moulitsas Zuniga on the Colbert Report (12 MB)
Audio-Markos Moulitsas Zuniga on the Colbert Report (MP3 - 8 MB)
He's got new book out called
Crashing the Gate