Osteria del Gatto
Not far from the above Nonna Gina. Menu will be in Italian but the waiters and the cooks will be available for a translation "on the fly". Fish is served one week a month. If you happen to be there in that week, don't miss the "Tonno alla Mediterranea" tuna fish in the Mediterranean way.
Osteria Sotto le Fonti
Restaurant off the beaten path, with owners who serve you personally; the waitress speaks fluently English very rare in Italy and knows how to recommend you wine, as she is also a wine tour guide. Is a pleasant walk downhill shortly outside the gates of the city, allowing you to look up at the top of the Duomo.
Trattoria I Barberi
(http://www.trattoriaibarb...) serves excellent typical tuscan cuisine and can be found near the duomo. it is also conveniently open every day from 11am to 11pm. if you visit during autumn, the tagliolini with black truffles is a must. address: via stalloreggi.
Excellent gelato can be found just off the Campo at two gelaterias called "Il Gelato" and "Brivido". Ask for Romaney at "Il Gelato"
For something more substantial, "La Chiacchiera" next to the House of St Catherine is an excellent source of typical Tuscan cuisine; the pici thick, homemade noodles are superb.
A unique kind of dense cake, made of honey, flour, almonds, candied fruits, a secret blend of spices, etc. tipo margherita is not the classic; it is a 19th century variation with less spice and more sugar; several other types are made. panforte is commercially manufactured only in siena and neighboring monteriggioni, its loyal ally in medieval wars with florence. the most famous brand of panforte is sapori. you can buy panforte most cheaply in local supermarkets, but don't miss a trip to nannini on banchi di sopra see above, a pleasant caffé where you can buy not only their panforte by weight but also many other types of unusual pastries and so forth.