My wife and I looking for a nice hotel in Florence. Our budget is $150 USD per night
The Bellevue House was great!
http://www.bellevuehouse.it/inglese/bed_and_breakfast_florence_center.asp
The location was convenient and the rooms were spacious. Friendly staff!
I always stay in the Hotel Casci. The Lombardi family really makes you feel welcome. It is located on Via Cavour near the Mercato Centrale just a block from the Duomo.