B-Ticket is the (allegedly) official site for online tickets for the state museums of Florence (which include most of the big ones you probably have heard about - the Uffizi, Accademia, Pitti Palace, Bargello, etc.). I only say allegedly because I have not been able to verify the site as "official", although it claims to be and I have read many people online refer to it as such. Anyway, if you want to reserve tickets in advance, this does seem to be the place to go. Check it out here: http://www.b-ticket.com/b-ticket/uffizi/default.aspx
