Conlangers and linguists should enjoy the interesting dialect maps at http://projetbabel.org/vosgien/langues_oil.htm:
Best not to dwell on the Microsoft Paint airbrushing. I find such maps fascinating; I once started to make a series of them for Verdurian, but never finished them.
What amazes me is the sheer variety in a relatively small area (the width of France is about the same as Illinois + Indiana + Ohio). And if you compare maps, each lexical item has its own story… the isoglosses don’t match up except in very broad terms (there’s often a northwestern-coastal area and a northeastern area). It’s also notable that Paris doesn’t seem to influence the patois all that much. (That is, standard French may replace the patois, but while they exist they retain their own particular words.)