Rather untechnical video on American regional and socio-economic dialects. It's been on tv a good many times during the past several years. It's light, entertaining, and clearly introductory rather than deep, but it's also accurate and educational. I recommend it highly for introductory classes. She played a character named Flo, if memory serves, on the old TV show 'Alice'.
Length is about an hour.
It is very clever, witty, and infuriating. The first part contrast regional dialects and some of the historical reasons for the differences. The second part deals with the social costs and consequences of these differences. I use the video regularly with my ESL classes. Other teachers are obviously using it also, I have to reserve the film in advance.