Athens Airport car rental options include Avis, Budget, Europcar, Hertz, Sixt, and Alamo through their Greek car hire partners National Car Rental.
All these companies currently have offices at the airport itself, although other companies will deliver cars to the airport to greet you on arrival so you should still shop around for the best deals. To check current details of car rental companies at Athens Airport visit the Athens International Airport website.
It's almost always better to book your Athens car rental in advance, both to save time on arrival and to be sure a car is available. In busy periods not all companies may have hire cars there. In any case, renting on the spur of the moment will be more expensive than booking your rental car online or over the phone in advance.
Something else to watch for is that not all the companies with airport offices are there 24 hours, and there may be extra charges to pick up a rental car or drop it off outside of normal office hours. Check before booking any rental car.
Athens Airport Car Rentals is a car rental company based close to the airport in Ano Glyfada and which will arrange to collect and return cars at the airport for you.
An account of driving in Greece for Greece Travel Secrets including links to the best drives in Greece, practical information and a note of some of the hazards.
This Athens dining guide doesn't list restaurants but gives practical advice on types of eating places, tipping, hotel breakfasts and picnics.
Spetses in the Saronic Gulf Islands of Greece is an easy day trip from Athens and has some good beaches. This page gives details of ferries and what to do.