We stayed this past May for 3 nights at a wonderful farmhouse B&B/agriturismo just south of Siena called il Canto del Sole in Monteroni d'Arbia (near Cuna), just south of Siena.
Highly recommended – charming hosts, great rooms, good food, beautiful location. It deserves its stellar reviews and ratings on tripadvisor and was a good base for nearby Siena and for exploring the countryside and hill towns south of Siena.
http://www.ilcantodelsole.com/inglese/index.asp
Also noteworthy right down the road from this B&B was the restaurant recommended by the innkeepers – the Osteria Il Contedino restaurant adjacent to the Hotel More Di Cuna. Beautiful inside, delicious simple traditional dishes using fresh local ingredients, great "vino della casa", good prices.
Driving between the hill towns of Montalcino, Pienza, and Montelpuciano through the Valley d’Orcia was knock your socks off beautiful – prettier than the California wine country. Then, the drive north between Siena and Florence up through Chianti was also quite stunning. More details and photos here:
http://www.virgin-islands-on-line.com/f ... 7&start=15
Some tips regarding driving in Italy:
• you WILL be tailgated and you WILL be passed anytime, anywhere - on curves, hills – it doesn’t seem to matter

However, I must say that most of the time the drivers doing the more aggressive passing are pretty skillful at it

The scooters in and near the cities are much more of a menace
• Out in the countryside, be prepared to navigate many many traffic circles (known as a “rotary” in Red Sox nation) at most intersections so as you approach your copilot needs to scope out which “spoke” out of the circle the driver will be taking via your GPS and the road signs
• Speaking of the GPS, here is what I did – it’s somewhat tedious, but I brought my own GPS with me, and I purchased the GPS map of Italy on SD memory card that plugs into my GPS (it was about $60, kinda pricy but so was renting the GPS with the car, and who wants to spend any time on vacation being lost?), then I preprogrammed the GPS with the hill towns we wanted to visit using the actual longitude/latitude coordinates rather than the names of places for better accuracy and to eliminate confusion with similar named places or misspellings. I did this by cross referencing online road maps from
www.viamichelin.com with the coordinates from google earth.
Being a “map person” with a decent sense of direction this process helped me visualize things better before I got there. I dislike depending entirely on the GPS and not actually knowing where I am or where I am going

. In certain situations I will trust my sense of direction over what the GPS is telling me – but that’s me. I also purchased and used the Michelin paper map of Tuscany (Toscana 358) as backup.
Its pretty hilarious the first time you hear the GPS lady describe the roads you are driving on – they can't just say “route 222”, they say something ridiculously long like “la strada de la something-or-other-via-something-else”
When you go to Siena you park in one of the lots just outside the city and take a shuttle bus up into town. In the smaller hill towns there are also lots to park in just outside the city walls to walk into town.
As noted on Anthony’s Florence website and elsewhere, don’t bring your car into Florence – too many nightmare stories of traffic tickets associated with trying to navigate the ZTL, or "Zona Traffico Limitato". We literally dropped the car off at the airport and took a cab into town for our stay in Florence. Florence is very compact and quite walkable, assuming you are reasonably fit.