What you can do in Lima (port is Callao) depends on if you have a full day in port or one afternoon and morning. We had two half days and the following is recommended:
1. Gold museum (Museo de oro) - a must see with all its pre-Columbian art.
2. Larco Herrera Museum and Indian Market - very interesting museum, also contains an erotic section of statues "guaranteeing" fertility in the next life and left in the grave.
3. A full day can get you to the Pachacamac Inca Ruins, however, read the reviews as a lot of sections are closed and the dust may turn you off.
4. At the wharf enjoy the free Wifi at the Peruvian market as the ships internet is very dear and very flakey and shop for souvenirs there.