New York Tech Meetup (now the New York Tech Alliance) - https://nytm.org/ (meetups happen monthly; events happen regularly, check the site for the schedule)
Co-working spaces in NYC - there are new ones popping up (and shutting down) all the time throughout different parts of the city. Probably easiest to search for co-working spaces near where you live. I haven't been to any in awhile, but a Google search should get you a decent list.
New York Tech Week - http://techweek.com/newyork-schedule/ (this happens in the fall, but you can still get an idea of popular companies and people from the speaker list. More of an information source.)