In Canada we poke fun at Newfies (people from Newfoundland) the most. At least I know we English-speaking Canadians do, French-speaking Canadians probably make of us the most.
I read that Polish jokes were turned into blonde jokes when people started finding the Pole jokes too offensive. Which is strange since it stereotypes all blondes as being dumb. And it's always blonde women. Never blonde guys. Of course there are jokes that make fun of *all* men, so...
And I'd be lying if I said I never found blonde or Newfie jokes funny, just because it's hard to picture anyone in real life that incredibly dumb, no matter what their gender/hair color is. 
Like the one about three blonde ladies who all want to become police officers but only one job is available at the station, so all three of them go to the same interview. The chief looks them over over and says, "Okay, since all three of you want to join the police force and there's only one job available, you'll need to each take a test. The first one who passes will get to stay and continue the interview, but if you fail you'll have to leave. Understand." All three blondes nod slowly. Then the cop goes and pulls out a file that has the mug shot of a recently captured criminal.
"One thing you have to be good at as a police officer is to be able to notice and identify unusual things on a suspect's face in only a split-second, like scars or moles. Okay the test begind NOW". He holds the photo of the man's face close to the first blonde's face, holds it for about two seconds, then whips it away. "Okay, can you tell me what was unusual about that man's face?"
"Sure!" said the first blonde, "He only has one ear!"
"NO!" Yells the chief. "Can't you tell that's his profile? You can't see his other ear because it's on the other side of his head! You don't get the job, lady!" So, the first blonde walks sheepishly out the door.
The chief then holds the photo up close to the second blonde's face for two seconds, pulls it away, then says "Can *you* tell me what was unusual about that guy's face?"
"It's obvious", says Blonde Number Two, "That he has only one eye!"
"NO!" screams the chief in exasperation, "Didn't you hear what I said to the first lady?! You can't see his eye because it's on the other side of his head just like his ear! You don't get the job either, so OUT!!"
Embarrassed and disappointed, the second blonde walks tearfully out the door.
The chief let's out a huge sigh and says "I'm not even sure why I'm doing this, but..." he holds the picture for two seconds in front of the third blonde, and then takes it away. "Okay, tell what was unusual about him" he grumbles.
Blonde Three says "He's wearing contact lenses, sir."
The chief stares at the photo, but of course he can't tell just by looking if the criminal really does have contacts on or not, so he goes back to the filing cabinet and goes through the info they have, and it turns out the man really does wear contacts.
"Amazing!" Exclaimed the chief. "How were you able to tell he was wearing contact lenses?"
"Well DUH!" exclaims Blonde Three, "He can't wear glasses if he only has one ear and one eye!" 