In my past experiences running on trails, the paths are demarcated for hikers and bikers and I learned about these running-appropriate paths through word of mouth and in person park information. After moving to New England and the New York area, I haven't been able to discover a definitive resource for finding wooded running trails that include some information and reviews about the path and surrounding area. Does a resource like this exist describing running trails in this area? If not, how do I find running appropriate trails?
I have not seen information regarding trails specifically from a running perspective, but there are a number of sites with information on hiking trails. Most trails suitable for hiking can also be used for trail running, and most trail reviews will cover sketchy sections which will be even more important if you're running.
I am not in New England, so I cannot vouch for the accuracy for any of these sites.
http://www.mountainsummits.com/homepage/mountains.htm/: Information on mountain summits in NE.
http://www.hikingnewengland.com/: Forums specifically on hiking in NE.
American Trail Running Association keeps a list for every state. It's not an exhaustive list, but it has some details for running.