Guided tours from Siena

There are a few, but they were very expensive (like 300 euros per person per day) so we simply rented a car from Avis for the day and visited Montalcino and Montepulciano on our own. The car rental, including extra insurance and the gas, was less than $150. On another visit we rented a car from Hertz and went the other direction, Volterra and San Gimignano. Hertz was a little more expensive and had some hidden costs so be careful whenever and wherever you rent. I always make reservations for the cars before we leave the U.S. Driving in Italy is not difficult but I do show respect for the people behind me - if we're slowing down to look at the scenery, I'll pull off the road completely so everyone can get by. And they appreciate that.

We took a tour with Roberto (https://sites.google.com/site/toursbyroberto/our-tours/half-single) and really enjoyed our day in Chianti. He picked us up at our B&B in Siena and returned us there that night. No worries about drinking and driving, no worries about getting lost, a fun and educational day. €90 per person. (Sorry about the link. Can't get it to embed.)

That's a great price - might have gone for that!