There are regular bus routes between Dubrovnik and destinations all over mainland Croatia, with hourly buses to Split, 14 daily to Zagreb, and 4 to Rijeka (Kvarner). Within the Southern Dalmatia region, there are a couple of buses daily to Ston and onward to Orebić on the Pelješac Peninsula, which continue to Korčula. Regular local buses run up the coast to Trstenik and down the coast to Cavtat (you can also catch the bus to Cavtat at the bus stop near the cable car). Remember that if you're traveling between Central and Southern Dalmatia by road, you'll pass through a narrow coastal strip called Neum, which belongs to Bosnia-Herzegovina, so have your passport at hand for the border checkpoint. Most Croatian buses have a 20-minute stop here so people can jump off and shop, since many things are much cheaper in Bosnia.
Dubrovnik Bus Station. Obala Pape Ivana Pavla II 44A, Gruž, Dubrovnik, Dubrovacko-Neretvanska, 20000. 060/305–070; libertasdubrovnik.hr.