Online resources such as Untapped Cities (untappedcities.com), Atlas Obscura (atlasobscura.com) and Forgotten New York (forgotten-ny.com) publish detailed posts on New York City, such as “The Top 10 Secrets of NYC’s Floyd Bennett Field.”
Meetup walking groups are an excellent resource, including walks previously posted by Shorewalkers that are no longer in rotation.
For trail hikes, the New York New Jersey Trail Conference website (nynjtc.org) has an interactive guide to choose trail hikes in New Jersey and New York.