The W&OD bike trail runs right thru Reston (Reston Town Center is about Mile Post 18-18.5). Reston Bike Club has a "no drop" A/B ride that leaves from W&OD Mile Post 20 (for Google maps - use Crestview Ave & Bond St Herndon, 20170 zip code)
www.restonbikeclub.org. They also have a spirited Tuesday night ride from Reston and a Thursday nite from Herndon (near W&OD MP 20). PPTC has weekend rides all over the area -
www.bikepptc.org. The Bike Lane's Reston shop has a shop ride from Reston Town Center -
www.thebikelane.com, and Trails End Bikes (Purcelville) may have something going on (west end of W&OD MP 45, so it's a haul from Reston!). You might also ask in the SouthEast forum and check the Road Racing forum - there are a number of NoVA riders there. Worst comes to worst, get to the W&OD and head east or west! (just watch the strollers, joggers, kids on training wheels, and cars at the street crossings). Hope this helps.