An audio map of US dialects NOV 26 2013
You've likely seen the various dialect maps of the US...the Coke/soda/pop maps. The Atlantic Video team did a wonderful thing with them...they called native speakers around the country and asked them to pronounce some of the words featured on these maps.
It's one thing to read the difference between the pronounciations of "route", it's another thing entirely to hear them. I haven't lived in the Midwest since 2000 and I have since transitioned from "pop" to "soda", "waiting in line" to "waiting on line", and am working on switching to "sneakers" from "tennis shoes" (or even "tennies"). But I was surprised to learn that I still pronounce "bag" differently than everyone else!