We will arrive in Siena December 30th and will use that as our home base for the next 4 days. We plan to visit Orvieto, what else do you recommend? Where should we ring in the New Year at? We will not have a car. Any restaurant recommendations?
By all means, rent a car and see the rest of Tuscany if the weather's okay. Many other hill towns are not to be missed, and it's just too difficult without a car. You can turn a rental car back in at Orvieto usually without any drop off fees. And by the way, Orvieto is fabulous. I wish we'd spent another day there. There are many sights 10-20 miles west of there. Their Hertz office is 75 yards from the train station.
Suzy, Siena is well-connected by bus or rail with several interesting places. You can easily get to Assisi, Cortona, Arezzo, without renting a car. As an example, Siena to Arezzo is about 1.5 hours by bus. Don't know about ringing in the New Year, but the Campo in Siena is probably a good bet, there's usually a concert.