A rich and informative site about the beautiful town of Massa Marittima and its environs, with extra info about the local cuisine and culture. http://www.massamarittima.info
The official site of the Manciano Proloco (only in Italian), has a guide about the town and general info about the surrounding area. Nice, especially the map of Manciano, does not contain lots of info. http://www.tuttomanciano.com