Do you have a car? If you like hiking, Path of the Gods is a as good as it gets. We started in Bomerano, hiked to Nocelle, took the stairs down and had a 3 hour lunch at Il San Pietro di Positano, then hiked back. Packed some nicer clothes in my backpack and changed in the hotel bathrooms. Definitely got some looks when we arrived sweaty after a 3 hour hike, but after a change of clothes and rubbing some rosemary from their bushes on those clothes, I was good to go. Also had sex on the hike back in an abandoned barn of some sort, so good day all around. Seriously, I can't recommend the hike enough.
We hired a boat in Amalfi to take us to Capri. I wish I had done more research ahead of time to find what to really do there, but we had a fantastic lunch at this place. Fresh seafood and good Italian wine looking at at Vesuvius? Yes please. Also got to swim in the Med on the way there and back.
Speaking of Vesuvius, if you are even remotely interested in history, Pompeii is fascinating. Maybe it's too crowded this time of year, I don't know. But we went in late September and it was awesome. We had a car, so all of this was fairly easy.