I agree with the person who suggested David Sedaris! He is definitely my favorite contemporary author. Don't read his books in public because you may not be able to contain your giggles, and you will look like a weirdo.
Augusten Burroughs writes a lot like Sedaris, but the humor is a bit darker, and I would definitely recommend any of his books. Who was it who said "Comedy is tragedy plus time"?
I'm currently reading "A Confederacy Of Dunces" by John Kennedy Toole, which is hilarious...it's a bit of a cult classic, even.
If you are a sick being and you like to laugh at tragic characters with disgusting personality disorders, read anything by Chuck Pahlaniuk. It's generally more schadenfreude than actual comedy, but I LOVE IT! Invisible Monsters is the best, IMO.
Happy reading!