Abandoned NJ - No actual excursions inside abandoned buildings on this weird site yet, as far as I can see, but apparently that's in the works.
Asbury Park - A history-minded look at the hotels, casinos, convention halls and other amusements of the abandoned Asbury Park.
East Coast Explorers - Site featuring abandonments from across New York, Connecticut and Pennsylvania, but mostly in New Jersey (currently down, hopefully temporarily).
Essex Mountain Sanitorium - Beautifully written fan site for an abandoned asylum in Verona, recently destroyed.
Midnight Society - Group of New Jersey-based explorers mostly focusing on "haunted" nonsense, but with a great section on abandoned buildings kind of hidden away. Could be a great site if they gave up the ghosts.
Nike Missile Battery - Fan site devoted to "a piece of Cold War history in Evesham's backyard".
Wanderer - Illustrated travelogues of some guys interested in abandoned buildings (mostly ruins) and weird and alleged haunted places.
Weird NJ - Mostly a silly site about "haunted" places, placing the emphasis on being scary rather than being realistic, but featuring a small section on abandoned buildings and the like.