GPS/Trails

GPS Trails
Use Google Maps and can upload GPX files:
 * http://www.wikiloc.com/ - Free
 * Google Maps, Free trails, GPX Upload, Public GPX View, ATV Trails
 * http://www.gpsies.com/ - Free
 * Google Maps, Free trails, GPX Upload, Public GPX View, ATV Trails
 * http://www.alltrails.com/ - Premium $30
 * Google Maps, Free trails, GPX Upload, No Free GPX Download, GPX View from Profile

Others:
 * http://www.traillink.com/ - Premium $30
 * Google Maps, Free trails, No Free GPX Upload / Download or View
 * http://www.trails.com/ - Premium $45
 * Google Maps, Free trails, No Free GPX Upload / Download or View

Potential Others

 * http://EveryTrail.com
 * http://OpenStreetMap.org
 * http://TravelByGPS.com
 * http://GPXchange.com
 * http://MapMyFitness.com
 * http://www.topografix.com/gpx_resources.asp
 * http://www.gaiagps.com/map/
 * http://www.viewranger.com/en-GB