I haven't got much, but here are two road stubs. They're for proposed extensions of the Seaford-Oyster Bay Expressway.
http://commons.wikimedia.org/wiki/File:NY135stubend.JPG

http://commons.wikimedia.org/wiki/File:South_NY_135_Stub-Exit_1E.jpg

Were it not for anti-highway zealotry, the road would've actually reached Oyster Bay. Not only that, it would've gone from Wantagh State Parkway towards Jones Beach, to a never built bridge across the Long Island Sound.
http://www.nycroads.com/roads/NY-135/
http://www.nycroads.com/crossings/oysterbay-rye/

Here's the abandoned Kings Park Psychiatric Center, part of which is in the Nissequogue River State Park:
http://www.lioddities.com/Asylums/Kings_Park/index.html

And some other abandones places on Long Island:
http://www.lioddities.com/Abandoned/index.html