Aegean Airlines is offering some great rates to Greece from European cities. You can book now until December 28th for flights departing on or after January 10th, 2010. Many of these destinations can be combined with cheaper flights from the U.S. or Canada. You need to book before December 28th to take advantage of some great deals on off-season flights to Greece; travel must be completed by March 28th, 2010.
From Barcelona, Brussels, Madrid, Munich, Milan, Rome, Vienna, and Berlin, it's just 55 Euros one-way.
From Paris, it's 66 Euro. For London flights, the most expensive of the bunch, the payment is in pounds - 69 of them to be exact. Here's a currency converter to help compare rates.
All fares include all taxes, but they are non-refundable and ticket changes are not allowed, so be sure this is exactly what you want before you book it.
Picture of Aegean Airlines plane © Aegean Airlines; used by permission.