Two Trail-Finder Links

https://www.hikingproject.com – for the hikers/backpackers

https://www.mtbproject.com – for the mountain bikers

These are the most comprehensive, user-friendly trail resources I've happened across to date.  They feature zoomable maps showing mileages & elevations, general descriptions, external links, and room for user input.  Good stuff, recommended!

BTW, they seem to be underwritten by REI, judging by the prominent links.  More power to them, it's top-notch advertising to make an overall useful site that also happens to mention your stuff.