Here you will find some itinerary recommended by Residence S. Francesco

Erice
Favignana
Levanzo
Marettimo
Marsala
Pantelleria
San Vito Lo Capo
Segesta
Trapani

It is possible to reach the following destinations from Trapani:

Naples (by ferry or hydrofoil)
Palermo (by coach)
Tunisi (by ferry)