The vast Pitti Palace complex includes several museums like the jam-packed Palatine Galleries where Raphaels' vie for space with works by minor artists--they'd be major artists in a smaller museum-- and the (not-so) Modern Art museum with a somewhat eccentric collection of 19th and early 20th century works. There's also the charming Porcelain Museum, the Costume Museum (not much there), and my favorite the Treasure Museum.
But best of all, especially if you've had your fill of grand museums and paintings, are the Boboli Gardens. The gardens, which cover over 11 acres, were first laid out for the wife of Cosimo de' Medici's wife, Eleanora of Toledo (you can see her portrait in the Octagonal room in the Uffizi).
These are very formal gardens, quite splendid and majestic. They also contain all kinds of ancient statuary and treasures including an amphitheater, an Egyptian obelisk, fountains, and a famous grotto. You can get a glimpse on this virtual tour. It's very pleasant to wander here and I highly recommend visiting (wear comfortable shoes!).
