My friend and I will be in Greece during the last week of July and are looking for budget hostel recommendations. We don't know specifically which area's we would like to stay yet but the area's we are most interested in are Crete, Santorini and Mykonos. Also if you know of any nice beaches in any of these area's that would be appreciated as well.
The organized Greek hostels are listed at http://athensyhostel.com/index.php/g-y-h-o. Greece has plenty of cheap, family-owned pensions, as well, although they may not be as cheap in high season as the €20 I've paid for a single in the off season. The Lonely Planet Greece book has been helpful to me.