We love wasting hours at the Speech Accent archive at George Mason University. Where else can you listen to the English accents found on the Mortlock Islands in Micronesia? The mad linguists behind this archive's recordings found someone to say, "We also need a small plastic snake and a big toy frog for the kids" purely for our amusement. Surely this archive would help Alan Ball make True Blood sound realistic. Listen in, and compare these real accents to what you hear in typical SF. [The Speech Accent Archive]
Hmm...this is an awesome project, but certain accents are not as indicative of their regional area as they should be. The Wisconsin accent, and the New Orleans, VERY established accents, are not half as thick as they should be for posterity. The UK accents are quite good though.
And, I'm from Fairfax, VA where GMU is located, and they recorded a male from Fairfax as well. His accent is, umm, not right. Its more just a Standard American, with some evidence of Southern dialect. There isn't really an "Fairfax" accent per se. Too many poeple coming and going in a county of 1 million+ will do that. (Although my uncle was convinced there was a DC accent....)