From Bologna airport to San Casciano in Val di Pesa
Bologna's Guglielmo Marconi airport (also known as Borgo Panigale) is at 118 Km (by car) from San Casciano VP. Bologna airport is served by low cost airlines like Ryanair.
With car
Rent a car in one of the rental companies inside the airport, then take highway A14 and then A1 (toll road) towards Firenze. Take exit Firenze-Certosa and then enter Raccordo Autostradale Firenze-Siena (RA03). Exit at San Casciano, turn right at Via Cassia per Firenze/SR2, continue on that road and you will be in San Casciano within 5 minutes.
Without a car
Option A (shuttle to Bologna Centrale, train to Florence, bus to San Casciano)
Take the shuttle service called Aerobus, it connects the airport to Bologna Centrale railway station in about 20 minutes. A one way ticket from/to Airport costs 5 Euro, tickets can be purchased on board too. Obviously to reach Bologna Centrale station from the airport you can use, instead of shuttle service, the taxi service. Once in Bologna Centrale, take a train to Florence (Firenze Santa Maria Novella).
There are three types of trains, from cheaper/slower to expensive/fast: regional, Intercity, Eurostar AV.
Regional
The trip lasts about 2 hours, you have to change in Prato, very cheap: just 6.75 Euro.
Intercity
It arrives in Firenze Rifredi, then you have to take a regional train to Firenze Santa Maria Novella; costs 10 euros, takes about 1 hour and 15 minutes.
Eurostar AV
Very fast train, but also expensive. One second class ticket is 24 Euro, the trip takes 37 minutes.
For timetable and details please refer to Trenitalia website.
Option B (bus only, to Poggibonsi then San Casciano)
Take a Sena bus from Bologna airport to Poggibonsi (less than 2 hours, price 5 Euro) and then a SITA/ACV bus from Poggibonsi to San Casciano. Please note Sena does only two trips a day (one in the morning and one in the evening).