Go to ports of call on cruisecritic to find out many suggestions of how to do this.
We did this trip last year. When we got off the ship there was a small tour office who were arranging trips to Pompeii and other places. As there were 6 of us they took us in a minibus to Pompeii, then Sorrento and around the Amalfi coast (beautiful) stopping at various photo spots. This was much cheaper than the trip off the ship and we were able to stop and spend what time we wanted at each place.
Hope this helps.