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/

Trail Runner Magazine Online

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

American Discovery Trail

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

Peak Trail Runner

A guide to trail running in the UK Peak District national park.
http://www.geocities.com/steviestoat/

Run Hayward Hills Trails

Trails of Hayward, California. Great for running and riding ATB.
http://members.tripod.com/sr_science/run_hayward_hills

Mountainrunning.com

Rocky Mountain trail guides with maps and descriptions. World mountain running trophy information on venues, maps, results. Guide to trail accommodations available.
http://www.mountainrunning.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/

BC Trail Running

Offers information on trail running in British Columbia, Canada. Includes articles, photos, and links to several trail series.
http://www.bctrailrunning.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

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

USTrailrunner

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

Perry Scanlon's Home Page

Contains photos and links to trail and workout information near Palm Springs, California, as well as specific information for the Skyline Trail.
http://www.geocities.com/cactus2clouds

Irish Mountain Running Association

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

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/

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/

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

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