The first annual "Florence Gelato Festival" is scheduled to take place May 28 to 31 in Piazza Santissima Annunziata. Gelato, tastings, workshops, etc. Unfortunately so far all the PR and advertising has been in Italian only, and even though there are posters up around town, and emails are being sent out, the website of the event (as I write this anyway) is still not "live": http://www.firenzegelatofestival.it/
In any case, it sounds great, and I really like the graphic:
We'll be there.