The Arlington Fun Ride is this Saturday. And it is really two rides in one
1) leaving at 8am, the full Arlington Loop (~17 miles) with pit stops; or
2) the Family Ride, run by Kidical Mass Arlington, meeting at 10am (3.5 miles, mostly flat). Both leave from and return to Crystal City (18th St S and Crystal Dr).
They need volunteers to marshall the ride and perform other tasks. I believe there is a T-shirt in it for you.