For a country that has no conception of irony, the US makes some damn funny sit-coms, although I'll stick with Peep Show and Inbetweeners.
Here you can find scripts for various episodes of 30 Rock, Big Bang Theory, and The Office as well as many more.
Check out the Pilots section as well, for a look at how hundreds of shows began their life. Some never got further than a script, others went on to be the biggest shows of their day. What makes one better than the other?