Potomac Pedalers has arguably the best catalog of cue sheets in the area. Take a few minutes to drop some into RideWithGPS.com, drop them to your Garmin and go! Printing cue sheets old school style works too. Rides can be accessed by starting location. Loudoun County High School, Marshall Park and Ride, Thurmont, Poolsville and many, many more provide great starting points for rides and there are many loops available at each of these places.
You have to join to see the cue sheets, but in my view the money is well spent. Their cue sheets are the only reason I stay a member.
Pete