Bikeride.com - http://www.bikeride.com/
Lists cycling related events from across the United States and Canada, plus a Web directory of over 1000 bicycling related sites, ride reports, blog, and cycling photos.
Ultra Marathon Cycling Association, Inc. - http://www.ultracycling.com/
Supports long-distance cycling including riding a century, double century, brevet, randonnee, or long-distance bike tour. Also promotes ultra cycling races and the cycling Race Across AMerica (RAAM).