Here are the updated combined summer ferry timetables for most of the summer, including sailings by Blue Star Ferries, Dodekanisos Seaways, and Sea Dreams Rhodes.
Correct to today, obviously subject to alteration if the ferry companies change their minds! There are notable extra sailings by Blue Star, giving two ferries a week each way to/from Kastellorizo, Tilos, Nissyros, and extra services to/from Rhodes, Kos, and Piraeus (Athens).