A nice site devoted to the film, It's A Mad, Mad, Mad, Mad World

http://www.povonline.com/MadWorld.htm

I would agree that it's not the best or funniest movie ever made.  But, my gods, the comedy greats who are present in it are incredible.  And there are some wonderful perfomances by Jonathan Winters, Phil Silvers and Sid Caesar.  Absolutely essential to anyone who is into American pop culture.