Here’s a map of North American English dialects from Rick Aschmann. It seems to rely heavily on Labov, Ash and Boberg’s Atlas, and there are a few of questionable judgments (e.g. labeling any region “General American”). It has some useful features that others resources might not: namely, he’s collected a number of youtube videos that illustrate various regional features. It’s a very interesting endeavor, and it deserves some scrutiny.