One of the most satisfying aspects of contributing to OpenStreetMap for me is walking a previously unmapped hiking trail, adding it to OSM, and seeing it appear on waymarkedtrails.org (and later in various hiking-oriented Android apps).
Recently I had the chance to survey a short waymarked trail that was completely unmapped (both the physical path and the waymarking). Here are the "before and after" screenshots from hiking.waymarkedtrails.org.

