Wine Town Firenze is this weekend, taking place in multiple venues in the center of Florence. Their website is a little weak, but this PDF has almost everything you need to know. For a list of producers/vineyards/consorzio represented, see this page. There is a lot of music and other events happening also.
One of the more interesting aspect of this event is that many of the tasting venues are in palazzos that you would more than likely never visit. Below is where you will find the wine: