New to this list: TheWashCycle.com
This site has really extensive coverage of "cycling advocacy in the nations capital" and related topics.
This links to their reporting on the Capital Crescent Trail, newest at the top, scroll down for older.
This is a "work in progress", a new website still under development. From one of the authors,
"The website collects and shares information on how to do the great long-distance car-free bike paths in North America -- where the paths are, narratives on their settings in nature and history, information on lodging and camping, restaurants and food, ice cream and beer, bike shops and shuttle services -- basically, what the touring cyclist would want to know to plan a trip that could be across the state or across the continent."
Worth a visit if only to see their page on the C&O Towpath.
Rails-to-Trails Conservancy is a nonprofit organization started in 1986, dedicated to enriching America's communities and countryside by creating a nationwide network of public trails from former rail lines and connecting corridors.
An organization dedicated to promoting a national network of trails. This website contains much information on building and maintaining all kinds of trails.
The largest bicycle association and resource in the DC Metro area. Their website has much usefull information on bike routes throughout the area.
Lists many rides and trails in the DC area, with good maps and ratings for terrain, traffic and scenery.
This Parks Division official website provides a description and map of all trails in the Montgomery County Parks.
Information and a detailed map of the W&OD Trail in Northern Virginia.
The site has info on C&O Canal history, current conditions and volunteer restoration activities, There is also info on joining the Association to help out.