My husband and I will be sailing on Liberty in October and after extensive research, have decided on the following:
Naples: Ruins of Pompeii (shorter; allows us to see our #1 pick for Naples while allowing us time to explore the ship some of the first day and schedule time in the spa). We also didn't want to book an Amalfi Coast tour and wind up in the rain... October can be unpredictable from what I hear.
Dubrovnik: Plan to explore on our own.
Venice: Gondola ride and explore some back canals and streets of the city. May decide to see Murano once we're there, but it's nice to have the extra time for 'what the heck, lets do it' activities.
Sicily: Taormina. I frequent http://www.virtualtourist.com
and when I asked what to see in Sicily, every single person (local and tourist) stated that it is a far better excursion than Mt. Etna for the time frame. I was also given good recs for local Messina restaurants.
Barcelona: I have friends here, so I plan to get together with them and see Gothic Quarter and Las Ramblas, Gaudi sites and Montjuic. I hear that this is one of the favorite cities, so give yourself time to go back to something for a second peek if you can. Tom should have lots of tips when he returns.
Cannes: We chose the Nice and Eze tour. I really wanted to see my idol, Grace Kelly's, grave as well as some of the harbour towns, but that may need to wait for a land trip to the riviera. It's a spendy tour and would take all day, but may be worth it for you.
Florence: Due to the distance from port to city, we are paying for the Florence on your own tour. This way, we have a guaranteed ride to and from (with no risk of missing the boat)and we can do our own thing in town. There is enough to see on foot in Florence that a broader tour may be a waste of money. We are choosing not to see Pisa this time, although we are in the minority on this decision.
Rome: We are spending 4 extra days in Rome, so the obvious sites will be on our list.
Have a great time! Post some info about the boat when you get back if you can!