I'm an amateur biker in the DC area and looking for some recreational/fun races and cruises?

I'm a 15 year old with a new Trek 7.3FX and am looking for some fun cruises with some people, and some fun charity races around DC and stuff. What website should I go to? I'm pretty good at biking, i've been biking for years, but not as good as others. I live in Arlington, and can take metro just about anywhere in dc.