There are two Western Union offices in Athens' Omonia Square that you can change money at or receive money from. They charge a fee for this. A percentage of the whole amount, about 7% I think. Greek banks will let you do this too but it takes longer and costs more. You can also wire EMERGENCY money via the American Embassy in Athens or its consulates elsewhere in Greece. For more info clik this link Money Wire c/o US Embassy Greece. Read this first!
Money to An American Overseas VIA US Embassy
8AM - 8PM weekdays; 9AM - 3PM Saturday
The State Department strongly encourages you to use commercial services, such as credit card advances, ATMs or Western Union. Locations of ATMs around the world can be found at http://www.visa.com and http://www.mastercard.com. Western Union services are described at http://wumt.westernunion.com/index_consumer.asp and 1 800 325 6000. These services are generally much faster than the State Department transfer system.
'If you cannot use a commercial service, the State Department will help you transfer money to a U.S. citizen suffering a financial emergency abroad. When you use this service, we establish a trust account in the recipient's name and send the money overseas. We charge a $30 processing fee. Remember this service is only for emergencies.'