The vintage shopping is pretty great in both cities. I remember Epoca in Florence and Twice in Trastevere.
Walking around Trastevere is cool as hell. Taverna Trilussa had delicious pasta and Roscioli was great for a mid-day bite
Drink lots of coffee and wine! Even the gas stations have good espresso.
If you have time, stop through Siena. Thought it was such a mysterious city with spooky nooks and winding maze-like streets. Half fort, half village.