The Mercatale di Firenze will be held in Piazza Santa Maria Novella on the first Saturday of the month, starting on April 5th, 2014. This market (if I am reading the Italian correctly) is the one that used to take place in both Piazza Repubblica and Piazza Santa Croce once or twice a month (sometimes there would be extra dates around holidays, etc.). There is no market day in August (of course!) but supposedly it will start up again in September and take place all year long.
Traditionally this has been a market full of Tuscan specialties and is billed as being "Zero Kilometer" - meaning that everything being sold is coming from very near Florence (or less than a kilometer away). Over the years we have bought wine, cheese, pasta, honey, spices, salami and prosciutto, amazing fresh vegetables, truffles, Nocino - you name it - just about all the wonderful things you could imagine eating that come from the region are available here. I would highly recommend a visit if you get a chance.
Here are a few photos from past incarnations (or similar markets - there are so many of these it is a little hard to keep track!: