If you don't have a washing machine in your appartment, if your hotel doesn't offer this service or whenever you need, here you can find all right addresses to solve this problem :)

You can choose between the two major companies that manage the wash and dry in Florence...

WASH AND DRY
Opening time: open all week long form 8.00 to 22.00
Address of the seven shops: Via dei Servi 105r, Via Nazionale 129r, Via de'Serragli 87r, Viale Morgagni 21r, Via Ghibellina 143r, Via della Scala 52-54r, Via G.P.Orsini 39r

ONDA BLU
Opening time: open all week long form 8.00 to 22.00.
Address of the two shops: Via degli Alfani 24-b/r, Via Guelfa 221/r

.. or if you prefer a local lanudromats shop.

BALDINI ENNIO
This shop does both regular washes and dry cleaning. For regular washes, the cost is calculated based on weight. There is an extra charge for ironing.
Address: Via Ponte Rosso 63/red
Phone: 055 472254

BRAGAGNI L.
This shop does dry cleaning and regular washing. The cost for a regular wash depends on the weight of the clothing you need to wash. They do not deliver. Their hours are Monday through Friday from 8:00 AM to 1:00 PM and from 3:30 PM to 7:30 PM.
Address: Via Boccaccio 75/B/red
Phone: 055 576036

LAVANDERIA PATRIZIA
This shop offers both dry cleaning and regular washing services. Regular washing prices depend on the weight of the clothes. They deliver clean clothes to your place of residence for free. They are open Monday through Friday from 8:15 AM to 1:00 PM and from 4:00 PM to 7:30 PM.
Address: Viale Volta 183/c
Phone: 055 571622

STIRERIA DI BOSCHI GIANNA
Laundry services in this shop include dry cleaning, regular washing, and ironing.
Address: Via XXVII Aprile 1
Phone: 055 2382004

Good Luck... and good washing :)