Borat: Cultural Learnings of America for Make Benefit Glorious Nation of Kazakhstan: Funniest movie of the year, certainly. I would rank this as being in the same league of funny as South Park, Team America, and Bad Santa.
I've seen some reactions that, I think, miss the point slightly. I don't think Borat is ultimately about exposing the "bigotry and ugliness" running rampant in America, though that is one element of it. I think Christopher Hitchens got it right: It's fundamentally about politeness.
We want to be polite to people, at least people as seemingly innocent and charming as Borat comes across, and to be tolerant of people from different cultural backgrounds. But the Borat character presents people with an insolvable dilemma: We want to be tolerant of other cultures, yet Borat apparently comes from a culture that is itself so bigoted and intolerant as to be, well, intolerable. You can see the tension in people dealing with this paradox, between the urge to be polite and accepting, and the urge to confront him. Frankly, I have more respect for the people who do confront him, and refuse to put up with his bigotry just because it comes packaged in a pleasantly innocent Latka-esque character. It's the folks who try to get along with him that end up pining for the return of slavery.