Our Adriatic cruise was Corfu - Venice - Portoroz - Sibernic - Dubrovnic - Montenigro - Corfu.
Venice is amazing, of course. With a smaller ship, you can sail up the Guidecca. We didn't do any of the ship's excursions. We made our way in and out of the city via very sleek James Bond style cruisers. We then just walked around, had lunch, did a gondola ride, bought some tat and returned to the ship. The sail-away was amazing.
I loved Portoroz. We took a ship's coach to the beach resort and just chilled on the beach. DH and the girls did watersports. We then had a really lovely lunch.
Sibernic was an interesting place - we basically walked around and then had lunch in the square, listening to our Bosnian waiter telling us how he was so hard done by. A lot of cruises stop at Split instead of Sibernic.
Dubrovnic is amazing and the scene of the civil war, We spent the morning at a beach resort where we had lunch and then took the bus to the city to see the buildings with bullet wounds. We took a cable car above the city which had the most amazing views. I think they could rival Rio. There was a supermarket opposite the cruise terminal where we spent the local Croation currency on crap that my daughter would throw up the next day.
Montenigro is the most impressive navigation through small channels. They resemble fjords. I had to stay on the ship with my sick daughter, but DH took the other two up a mountain. The town was a mini Dubrovnik
Corfu - when we got back to Corfu it was phenomenally hot. We basically couldn't do anything that wasn't in the shade - we had lunch, wandered the shops, stepped into an orthodox church, and returned to the ship for a quick drink before our departure.