I stumbled upon a very cool article from Genealogy Magazine's 2006 archives and thought you guys might enjoy it:
Surnames Sound a Challenge For Researchers
It's all about how Americans' pronunciation of surnames diverged a long time ago from how the names were actually spelled. I found it while searching for the correct pronunciation of "Beauchamp," since I have read soooooo many articles lately about The New Republic's military go-to guy, Scott Thomas Beauchamp. It's usually pronounced "Beecham" over on this side of the pond, apparently. The magazine folks compiled a nice list for us of names and pronunciations that aren't, well, intuitive.
I've been amused by the variation between spelling and pronunciation of proper nouns for as long as I could spell. Near the city of Paris in northeast Texas, where I graduated from high school, there's a small town called Bogata. The first time I saw it, I pronounced it like the capitol of Colombia: bo-gah-TAH. I was corrected immediately, for over there they say "buh-GO-tuh." But, I protested, it's not spelled the right way to say that. They misspelled it. Well, yeah, maybe they did. But this is how it is.
Another local community over there is Kiomatia... pronounced ki-MISH.
In Oklahoma, we have the Washita River. Next state over, in Arkansas, they have the Ouachita National Forest. It's pronounced the same: WAH-shih-tah.
It's not a trend peculiar to Americans, though. The English have some incomprehensible ones, starting with such obvious ones as Worcestershire / Woostershir. And how in the world do they get "Sinjin" from "St. John?"
If there are any odd ones from your neck of the woods, leave 'em in the comments. I love this kind of stuff.