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/

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

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/