Stand-up comedy is doing well these days. Variety cites the tough economic times, but I think it also has to do with accessibility. It's now easier than ever to watch or listen to stand-up - podcasts, satellite radio, cable, college tours, expansive city tours and YouTube have risen on top of the usual clubs, which can be a little pricey these days. There's also a significant undercurrent of alternative comedy, especially in New York and Chicago, getting more attention and stage time.
I think another factor contributing to this surge is how specialized the entertainment has become. Almost everyone can find a comedian or two that closely aligns to a particular sense of humor, from blue collar Larry the Cable Guy to skeptical transvestite Eddie Izzard, Jim Gaffigan to Mitch Hedberg (he's still popular posthumously), Demetri Martin to Mike Birbiglia to Jerry Seinfeld - there's someone or something for everyone. And this goes without mentioning the attention that the late George Carlin generated both for his career and his influence on others.
So while the "tough times" surely influence some of this, I think a lot of credit should go to new media and the people plugging into it.