Hi,
Thought I'd flag up these two superb podcasts as neither show gets much of a mention on these shores.
First, a link to a This American Life. The episode is entitled 'Tough Room' and is a fascinating look at what it takes to make an audience laugh. The middle story is worthy of special mention - where Ira gets an inside look at the editorial process at The Onion.
http://www.thislife.org/Radio_Episode.aspx?sched=1228
The second is a podcast is from social science show Radiolab. It's called 'Laughter'. I promise, it's nowhere near as drab as I make it sound. It deals with the physical process of laughter and why we humans need it.
http://www.wnyc.org/shows/radiolab/
Go check them out, you'll barely regret it.