Herculanium is the best. And Pompeii, of course, but this time we did the Villa Poppaea in Oplanta. A large summer house of one of Nero's wives. The walk to the Circum Vesuviana station is quite doable.
there is a bus station right at the terminal and a large grocery store called Konzum next to that. Take bus Number 8 to the cable car, 1, 1a, 1b, 3 and 8 to downtown. 12 krona fare. Cheaper than what the boat offers, and more convenient (if you are going to take the cable car, at least). Make sure you read which bus stops at which stop coming back.