Evolution - The American Dialect Homepage

http://www.evolpub.com/Americandialects/AmDialhome.html

Website hosted by Evolution Publishing. It has a link for a map of the Linguistic Geography of the Mainland United States that puts together maps made by different linguists. The latter is divided into New England Dialects, New York Dialects, the Great Lakes Dialects, the Upper Midwest Dialects, the Midland Dialects and the Western Dialects. It provides some general features of each variety but there are no audio samples. It also has a map for the Linguistic Geography of Pennsylvania, which divides the region into eight dialects: Hudson Valley, Anthracite Region, Central Pennsylvania, Upper Susquehanna, Lehigh Valley-Berks County, Lower Susquehanna, Delaware Valley and Upper Ohio Valley/Western Pennsylvania. This map also presents some general features of each dialectal region, but not enough to really describe distinctive dialects.
There is also a bibliography on the subject, an article on Ebonics and links to many websites, mostly made by non-linguists, but some of them do not exist anymore.