Cyclades (too far to visit on charter, but an easy high speed ferry trip)
Kimolos
Naxos
Milos
Sifnos (this island is close enough to visit in good conditions but is one of my favorite islands.)
Requires a short flight or long ferry
Kos (Dodecanesee island)
Rhodes (Dodecanesee island)
Kefalonia (Ionian island)
Crete (Large island with tons to offer)
Saronic
Nafplio (Usually too far to sail to)