Dolmades (grape leaves stuffed with meat) is one of the first thing that comes to mind, when I think of Greek food. These grape leaves are generally vegetarian, but you can add ground beef for special occasions.
Tzatziki Sauce :: She learned how to make it while visiting Athens - this is the best way to make REAL authentic Greek tzatziki! I love that you can make it ahead of time and it just keeps getting tastier. Saving this one!