American Dialect Map
These are cheesy, but I found this "what American accent are you?" to be interesting: 
http://lewrockwell.com/spl3/american-accent-quiz.htmlI don't know if this map had such a quiz - I was looking for one and couldn't find it.  It's interesting to compare notes with the quiz if you work with people from across the US (what do you mean, "bag" doesn't rhyme with "vague"?)