Albany Running Exchange
   Trail running club based in Albany, New York. Includes summer trail run series, results, calendar, photos, and member news.
   http://www.albanyrunningexchange.org

All American Trail Running Association (AATRA)
   Membership application and extensive collection of links and information on events, trails, equipment, and race results.
   http://www.trailrunner.com/

American Discovery Trail
   Learn about the first running trail that crosses the entire nation.
   http://www.discoverytrail.org/

Gil's Athletic Club
   Trail running club based in Topsfield, Massachusetts, sponsoring several trail races (primarily ultras). In addition to race information, includes weekly runs, guide to area trails, and photos.
   http://www.gaconline.net/

Irish Mountain Running Association
   Irish mountain running. Trails, races and links on the Island.
   http://www.imra.ie/

New England Trail Runner
   Extensive listing of New England area trail racing and running information on the web. Includes race results posting and trail running club information.
   http://www.newenglandtrailrunner.com/

Northern Arizona Trail Runner's Association
   Promotes trail running in Northern Arizona, in the United States. Contains a listing of upcoming races, related links, history of the organization, pictures, membership details, race summaries, and message board.
   http://www.natra.org/

Redwood Trails
   Information on a series of trail runs in the Bay Area of California. Race distances range from 5k to the marathon.
   http://www.redwoodtrails.com

Shenipsit Striders
   Trail running club in Somers, Connecticut, sponsoring the Soapstone Mountain races as well as weekly training runs. Includes race information and results, photos, and links.
   http://www.shenipsitstriders.org/

Team Gloucester
   Trail running club in Gloucester, Massachusetts. Cape Ann trail information and maps as well as an extensive trail race calendar for New York and New England.
   http://www.teamgloucester.com

Trail Runner Magazine Online
   Running, health, travel, and training, race results and race event calendars.
   http://www.trailrunnermag.com/

USTrailrunner
   Includes gear reviews, race calendar, online store, and discussion board.
   http://trail.ustrailrunner.com/

Western Mass Athletic Club
   Trail running club in western Massachusetts. In addition to club news, includes information for several trail and snowshoe races as well as the Grand Tree Trail Race Series.
   http://www.runwmac.com/

eHow to Choose Trails for Trail Running
   Tips and information about trail running. Requires free membership.
   http://www.ehow.com/how_14503_choose-trails-trail.html