Michael Feldman will be featuring Joan Hall, Chief Editor of the Dictionary of American Regional English, on Whad'Ya Know? this morning. (The url is easy to remember: http://www.notmuch.com/.) It's on at 10:00 local time, and they post the show within a day or two at notmuch.com.
The great Frederic Cassidy was on years ago, and a couple of the Wisconsin Englishes Project guys were on a few years back (audio available here).