If you are going to spend some time near Naples, you might like to investigate the Campania Artecard which can include free and discounted museum entrances and transportation (local, regional - Circumvesuviana and ferry - Metro Del Mare). It's quite a good deal. There's one card just for Naples and the Campi Flegrei area and one that includes Pompeii, Herculaneum and other archeological sites.

http://www.campaniartecard.it/ Choose English from the left hand menu.

Frances Toronto, Canada