This site contains an archive of accents from around the world. Each speaker reads the same paragraph in English.
The American accents are either very good or bad. The one from New Orleans sounds like she is from the Midwest. Where did they dig her up? Not out on the bayou, that's for sure!!
The woman from Brooklyn and the one from North Carolina are the most representative of their area, to my ear. It's very cool to hear the subtleties within America and also in Britain. It looks like they are still building the archive so lots of places are not represented yet.