It partly depends on the kind of comedy you like. I tend to go for the increasingly insane farce, where you get punchdrunk, which is hard enough to keep the bubble going on a stage, but to do it writing is hard, hard, hard --

(1) Catch 22 is the funniest book ever written;
(2) Several of Mark Twain's essays are insanely funny, especially when read aloud -- the two best may be "The McWilliamsons and the Burglar Alarm" and "The Great French Duel";
(3) One or two of S.J. Perelman's stories move into the insane bubble;
(4) The films, Twentieth Century, His Girl Friday, and Bringing Up Baby all have the same supersonic nutsy quality some of us love.

yours,

Peter T.