Around 15:20, he talks about jokes that are "brushback pitches."
I like jokes that are brushback pitches. There's a mix of laughter and people going, "Oh, Jesus!" But that turns into laughter. I like taking people to an area in their minds or their culture that they don't think they should be thinking about or laughing at, and then getting them to laugh there. That's a great thing to be able to do that. Take people to a place they're afraid of and say there's something funny here.
The joke he mentions is a 9/11 masturbation joke (it's in his latest special "Chewed Up"). Unconfirmed rumor I heard: He actually got kicked out of the Cellar once for telling it.
I watched "Chewed Up" the other night and really enjoyed it (stronger than "Shameless" I think). The fact that he's churning out a new hour every year is just incredible. It's all the buzz among comics. How funny he is + how prolific he is = he's definitely the one setting the bar right now.
If you haven't already, check out the video section of his site. Two of my faves there: Kansas City 11/05/04 and Largo 7/12/04.
The Comic's Comic has an interview and a good roundup of recent CK links around the web and Dead-Frog just published an interview too.