We're not to far from each other. I have about 4 places that I usually ride within 2 hours of my house.
1.) Potomac River Trail - This trail should be ridden at your own risk...you can start from the commuter lot in the K-Mart parking lot on Dale Blvd. in Dale City and ride all the way to the Potomac river. The only problem is that you must cross Cardinal Rd., RT 1, and 2 other back roads. I have ridden this trail several times, and have had no problems. Trail length: 10-15 miles one way.
2.) The Land Between the Lanes - This trail is also ride at your own risk...you can start from a gravel lot just off RT 1 south of Aquia, VA. The parking lot is just past a mini golf place, and past the bridge over a creek on the right at the bottom of a hill off RT 1. If you follow this trail it will eventually lead you to a tunnel under I95 south to the median. The median here, and south to the RT 630 exit (Stafford) can be ridden. It's actually a great trail. Once you get close to RT 630, you can cross back under I95 south and ride further. Trail length: 12-15 miles one way.
As for the 2 other trails, they are at least 1 hour away, but completely legal, so let me know where you ride, and if you're interested in riding these trails too.
See ya,