Calamari to go
Mid-Atlantic - Passport DC
May 5 is the open house day for the Asian, African and South American embassies.
May 12 is Shortcut to Europe, when the EU embassies are open.
There is no official bike ride that I'm aware of. For the past few years I've ridden the embassy circuit, eating, picking up free stuff, enjoying the entertainment. I've only done the EU tour, so I can't speak about the others. Particularly good parties from past years were at the German, French, Swedish, Finnish, British, Austrian and Czech, although the Belgian, Polish, Hungarian and Spanish are also worth a stop.