Today I think I hit the mother load!
Go to goby.com and where it says what you want to do - type in "free" and for the place type in "NYC" - leave the when as "anytime". Wow.
If you can wade your way through the gluten-free restaurants that pop up - there is so much free stuff going on. Nightclubs every night FREE for simply using the Forbidden List password, free drinks, free night time bike rides through Central Park and on it goes. It all seemed current info as well.
It's a nice little search engine they've got going on down at team Goby.
Oh and when you are sick of free stuff in NYC you can get out of there for FREE to Hartford Conn. or Amherst, Mass with megabus.com - Use promo code NEWNYC for free tickets to or from New York City (thaks to Travelzoo)