I brought it up in this post when I read that critics thought Hillary Clinton was using different accents on purpose when she was actually doing what a lot of people do unknowingly- code switching which is adapting one's accent to those around them.
Holy Dipthongs, Batman.
In today's Newsday, Taw-kin' Lawn Guy-land, the local accents are explained by dialect coaches. It pretty much sums up what I had always thought- that it's more ethnic than geographic. There is no one definitive Long Island accent because it's based on Italian, Irish, Jewish or Hispanic. Tony Danza doesn't sound like Rosie O'Donnell or Billy Crystal or Rosie Perez. It's all quite interesting here in the ol' meltin' pot.