North American English Dialects Map
This is a map created by Rick Aschmann which details the different dialects spread out across North America. Alongside the map, there are also many videos of people submitting their own speech and his commentary on some of them. There is also a chart to help differentiate between different dialects. For me, one of the most interesting things about the map was the big unified bloc on the Western side of the United States compared to many different dialects over on the Eastern side.