The first thing many are concerned about are the laws of riding around the Nation's capital. There are portable resources listed below for your use.
A Nice Community Member made a smart phone ready page: http://bit.ly/bikelawdc
District Department of Transportation PDF: DDOT Pocket Bike Law Guide
*UPDATE: The mobile apps give you great insight into what cops might forget, egal council, emergency contacts, etc.
Side Note: Did you know there's bike insurance now? Aimed primarily at commuter or daily riders it seems. But it makes sense.