Florence marks the beginning and end of November with a huge historical date and an international sporting event: the somber remembrance of one of this cities worst tragedies, the epic Flood of 1966 on November 4th, contrasted by the lively Firenze Marathon, traditionally held near the month's end.
In between there is the annual Olive harvest in Tuscany and usually plenty of chances to taste the first fresh pressings of the year. One of the best usually takes place in Pizza Santa Croce, the "La Rassegna dell’Olio di Reggello".
November also brings the nearly month long White Truffle Festival (La Sagra del Tartufo Bianco) in the hill top town of San Miniato, along with dozens of other events and happenings (info here in Italian - runs into December).
Depending on the year the ceremonies that mark the anniversary of the flood can be quite large (like on the 40th in 2006) or so lowkey it is hard to find to find out what is happening unless you can speak and read Italian. What you will probably see all over town are shop owners hanging their photos from that fateful day, especially in the hardest hit areas like Santa Croce - many are probably already up so keep your eyes open!
As to the Marathon - if you plan to enjoy it remember one thing: stay out of the way! And if you are just visiting make sure you draw a circle around the date this year - the town is pretty much shut down. You can forget driving anywhere until well after dark usually, and most of the streets are closed all around the center of town and beyond for several hours starting early in the morning. Use public transport where available, or either plan to just spend the day in the city or out.
And don't forget to bring you umbrella in November and something warm to wear - the weather can change quickly this time of year, and the rain can be torrential!