As of December of 2007 from Dulles:
Aeroflot - Moscow/Sheremetyevo
Air France - Paris/CDG
Aer Lingus - Dublin
Austrian - Vienna
British Airways - London/Heathrow
Iberia - Madrid
KLM - Amsterdam
SAS - Copenhagen
United - Amsterdam, Brussels, Frankfurt, London/Heathrow, Munich, Paris/CDG, Rome, Zurich
Virgin Atlantic - London/LHR
Obviously, DCA has zero. You can't even fly to the west coast nonstop.