Lucca. You can travel by train to this other beautiful Tuscan city.
Florence. Very easily reachable by train from Pisa Centrale.
Cinque Terre by train to La Spezia and Genova
Volterra by bus
Calci is very easily reacheable by bus. A charming medieval village nestled in the Pisan Mountains. The Charterhouse of Calci and the Museum of Natural History home to the largest collection of whale bones in Europe are among its attractions.