day trips from Florence

Siena is an excellent destination. I suggest taking the bus (terminal is near the S.M. Novella train station) for a more scenic ride. It will let you off within easy walking distance to where you want to be. Lucca is also a possibility, by train, but a bit longer.

Lucca is perfect, only an hour by bus or train. A flat Tuscan town will lots to see and do.

I also love Lucca, though think it's more like a 90-minute train ride from Florence. I've been several times and love it. You can walk around the wall, or rent a bike and ride around it, or do both!

A brief stop in Pisa for the leaning tower is possible before heading on to Lucca.

Some train timings for example.

RE 3111
Dep 08:28 FIRENZE S.M.N. (Italy)
Arr 09:28 PISA CENTRALE (Italy)

RE 6761
Dep 12:20 PISA CENTRALE (Italy)
Arr 12:47 LUCCA (Italy)

RE 3079
Dep 18:31 LUCCA (Italy)
Arr 19:50 FIRENZE S.M.N. (Italy)

Lucca and Fiesole are 2 towns that are worthwhile - Lucca is a train ride and Fiesole is an easy 30 min bus ride from Florence. There is an American cemetery (WWII soldiers) that is breathtaking and humbling and 7 miles south of Florence. The small hamlet of Vinci is within driving distance from Florence also, it is fascinating if you admire LDV and his machines and drawings.

Love Lucca! Siena is beautiful too but I would probably pick Lucca over Siena. As previous poster stated you can combine it with Pisa if you wish. Climbing the tower at Pisa was a great memory for our 2 boys. I returned here on a girl's trip with my sisters and climbed it again! Fiesole is an easy bus ride as is the church of San Miniato al Monte which you could combine with Piazelle Michelangelo where there are beautiful views over Florence. I know some posters on this board could recommend a company to do a daytrip to the Chianti region which would be fun too. We have driven the Chianti trail several times so can't recommend a tour company. Whatever you decide it will be amazing! Buon Viaggio!!

Fantastic info!
Would it be a good idea to buy train tix to Pisa and then Lucca ahead of time, or when we are there?

Thanks!

If I had to pick one: it would be Siena.
If you have time for 2 days out of your time being taken up by day trips: the Pisa and Lucca combo would be #2

The train tickets to Pisa - Lucca will not sell out so you can wait. Benefit to buying early is they may be less expensive to do so.
Since it is a day trip ; personally I would prefer to wait and play the weather and how you are feeling by ear rather than have a set in stone day ; your call though.

If Siena the bus is a better option than the train as the train station in Siena is not in the center of town like the bus is.

Tickets to Pisa and Lucca are regional trains, no need to purchase early they'll be the same price when you get there. You will need 2seperate tickets.

I am thinking about dropping Pisa and spending time in Sienna instead. Is Lucca a possibility the same day?

Siena is south of Florence and Lucca is west of Florence. I would strongly suggest spending a day in one or the other. Trying to do both in one day is not feasible, in my opinion.