La Giostra, Il Latini, Osteria di Cingialo Bianco, Camillo, 13 Gobbi....
If you use the search this board box above and put in Florence Open Sunday, it will pull up a list of about 13 places (two ringers and one gelateria) which have been tagged for this characteristic in the Chow Restaurants page - you need to click to expand the list at the bottom (havent had time to work through the whole Florence list to creat tags yet). Hope if any of the info is not current folks will correct it.
I don't know if it's too late, but we went to an old local favorite: Osteria Centopoveri. They do excellent pastas and seafood.
For a splurge of the best seafood in Florence (from the coast), we love Fuor D'Acqua. It's a nice place, but service is a bit patronizing to the non-local and they would prefer to do the ordering for you. If you don't mind, the freshness of the seafood is just amazing (from raw scampi and seabass to lobster spaghetti and branzino. We just went last night and had to be rolled out of there.