From Piraeus, Athens' port, you can take a ferry to the following Greek Islands/Ports (in alphabetical order) :
A
Aegiali, Aegina, Agistri, Amorgos, Astypalea, Ag.Kirikos
C
Chalki, Chania, Chios, Crete
D
Diafani, Donoussa
E
Evdilos (Ikaria)
F
Folegandros, Fourni
H
Heraklion (Crete), Hermioni, Hydra
I
Ikaria, Iraklia, Ios
K
Kalymnos, Karlovassi (Samos), Karpathos, Kasos, Kastelorizo, Katapola, Kimolos, Kos, Koufonissi , Kythnos
L
Leros, Lipsi
M
Methana, Milos, Mirina (Limnos), Mykonos, Mytiline (Lesvos)
N
Naxos, Nisyros
P
Paros, Patmos, Poros, Porto Heli
R
Rhodes
S
Samos, Santorini (Thira), Schinoussa, Serifos, Sifnos, Sikinos, Spetses, Symi, Syros
T
Thessaloniki, Tilos, Tinos
V
Vathi (Samos)