Alla Madonna del Piatto in Umbria near Assisi. One of the owners. Letizia is a friend of friends. It's an Agriturismo, B&B and there is a small apartment to rent as well. Letizia also offers cooking classes. It's not really a working farm experience, but it's not clear if you want to stay on a farm or work on a farm.
http://incampagna.com/