You may book your ferry boat tickets to Patras from the Italian ports of Trieste, Ancona, Venezia, Bari on the sea lines ANEK LINES, SUPERFAST and BLUE STAR FERRIES and from Brindisi though MED LINK LINES and HML.
There are corresponding boats from Patras to Cephalonia from BLUE FERRIES and AGOUDIMOS LINES.

You may also travel from Cephalonia towards: Lefkada, Ithaca, Zakynthos (Zante) and Astakos.