Unless something has changed since May 2007, the only tender port that we had on this itinerary was the one in Cannes, France. If you did not book an excursion there, you had to wait until all passengers with CARNIVAL excursions left the ship. We booked the Monaco Monte Carlo excursion, but due to a bus strike we had to take the train over and that took most of our time. One couple in our group, just got off the ship and took the train to Eze and went through some shops and spent the rest of the day on the beach. I wish we had done that instead of taking the excursion.
In Croatia, if you can get to Old Town it is a nice place to spend a few hours. We did the Carnival excursion of a Konavle farm home which was nice but not really worth the money. The scenery there is beautiful though.
In Messina, Sicily our group chartered a bus as a group and went to Taormina for a fraction of the cost that Carnival was charging and our group got there an hour ahead of the Carnival bus. Loved Taormina.
Venice, you can do on your own, but our group arranged for the second morning to take a charter boat out to Murrano and Burrano and we loved that as well.
We used Pappillion tours in Livorno. A guide picked up 6 of us in a nice mini van and took us to Florence with a stopover to see the Pisa on the way back. She made arrangements to for us to see the David and we walked right past the long line at the gallery, had a nice lunch and a very enjoyable day.
Been there - done that:
2005 Holiday, Sensation, Conquest,
2006 Conquest, Celebration, Holiday,
2007 Freedom Grand Med, Holiday
2008 Fantasy & Sensation,
2009 Fantasy, Holiday & Dream Grand Med
2010 Fantasy and B2B Elation
2011 Monarch of the Seas
2012 Booked - Breeze from Barcelona 12 days