Gelatiamo, the cute Italian gelato shop downtown, is celebrating May Day (and the completion of its recent renovation) today with free gelato from 11 a.m. – 1 p.m.I was there yesterday (of course!), and after a thorough sampling, I can report that hazelnut was my favorite, followed closely by pistachio and the dark chocolate.Gelatiamo, 1400 Third Ave., 467-9563, DOWNTOWN.I