I'd like to go from Palermo o other sicilyan city to Athens or some other city in Greece.
I'd like to know if available and all kind of information.
Thank you!
Check out rome2rio.com The flight options look like the best bet to me.
It's doubtful you'll find any non-stop flights from Palermo to Athens but I'm seeing some VERY CHEAP flights via Rome on the Airtickets website, some as low as USD $77, one way using Iberia Airlines. Of course the fare will depend on your travel date.
http://reservations.airtickets.com/airtickets/com/search.do?sid=5&xid=1443569277121
If you do end up flying, be aware that Catania (on the eastern side of Sicily) is actually a bigger airport than Palermo, with a wider selection of flights.
Other than ferries to the small islands around Sicily (Stromboli, Lampredusa, etc), the only Sicilian ferry I know of is the overnight one from Palermo to Naples. With the advent of budget flights, there's far less demand for ferries, even among budget travelers. But do check Rome2Rio to see what turns up.