At the official international Blue Flag site, at the right of the Greece page they have a list of Greece's Blue Flag beach regions which, if you are diligent on clicking through, leads to a close-up map showing exactly where each blue-flag winner exists.
3. Kamares 1 and Kamares 2, Santorini (Thira)The volcanic island of Santorini has a rainbow of beaches with different-colored sands on each, the product of the tremendous eruption which shattered the island about 3500 years ago. Kamares, on the east side of the island, is famed for its black sands - and for its lovely water quality. The beach area is developed with many tavernas and small hotels, and its also near the mountain-top site of ancient Roman Thira. With the dazzling location, the local tavernas are a bit pricy but overall, Kamares is well worth a special visit.
4. The Beaches of Mount OlympusHuh? How can mountains have beaches? Discovering that is one more reason to make the trek to the Mount Olympus region, where the foothills are close to the seashore and the clean beaches are worthy of Zeus himself - who, if ancient stories are to be believed, probably makes regular visits to check out this year's crop of nymphs. The shores picked out by Blue Flag include Leptokarya 1, Skotina, Panteleimonas 1, Platamonas 1, and Pori. In this region, you'll find yourself in easy distance from Dion, the extensive ancient city founded by Alexander the Great and Litochorou, the jumping-off point for many ascents to Mount Olympus and the home of one of the best restaurants in Greece, En Olympo.
In 2012, two of Evvia's beaches have been noted by Blue Flag - Alyki Drossias and Eretria 3. Eretria also offers an extensive archaelogical site in the area.
Like large Greek islands? Here are the 20 Largest Greek Islands, in order of size.
6. Marathon Beaches, AtticaI love when beaches combine with history, and these two in the Marathon area allow you to design a day at the beach with a visit to the archaeological site and the very good small museum devoted to the sites. The two spots are Schinias/Karavi and Brexiza - Schinias was the site of some of the kayaking competitions during the Athens 2004 Olympics. Brexiza is the site of an ancient temple of Isis and other archaeological remains.
Fodele Beach is also known for another kind of visitor - in July, small dolphins are often seen in the waters around Fodele. The link above leads to a narrated slideshow from Yannis Samatas about Fodele.