Andrew of the WTA blog has a list of many fine hiking sites, most Washington-related but not all. A sample:

Abandoned
Trails
A detailed site by a hiker who’s fascinated with abandoned trails. This
is probably the best online guide to obscure, hidden hikes in
Washington state. If you’re curious to explore places like Koppen
Sheepherder Trail–and aren’t afraid of a little bushwhacking to leave
the crowds behind–this site is for you.

Topic for another day: pluses and minuses of bushwhacking.