All the sites are reachable in half an hour from the Naples train station by train, bus, highway.
Circumvesuviana - Naples - Sorrento
Circumvesuviana - Naples - Poggiomarino
Trenitalia Napoli Centrale - Pompei
More detailed information clicking on the name of the following sites:
Pompeii, Hercolaneum, Oplontis, Boscoreale, Stabiae