USTrailrunner - Includes gear reviews, race calendar, online store, and discussion board. - http://trail.ustrailrunner.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
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/
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
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/
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/
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
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
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/
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/
American Discovery Trail - Learn about the first running trail that crosses the entire nation. - http://www.discoverytrail.org/
Trail Runner Magazine Online - Running, health, travel, and training, race results and race event calendars. - http://www.trailrunnermag.com/
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/