There are tens of thousands of software developers employed in the New York metro area. This is not a reasonable approach to identify tech companies.

Artsy, Tumblr, Facebook, Twitter, Etsy, Kickstarter, Meetup.com

Full list: http://wearemadeinny.com/made-in-ny-list/

Full stack academy , Trello , Codeacademy ... These are the 3 start ups that come to mind .... I'll keep adding as I remneber more

DigitalOcean is based here. And like others have said, many companies are either started here or have a satellite office.

Google has a very large NYC office.

StackExchange.

Bond Street

Foursquare was originally hacked together at the Think Coffee near NYU. They are still based in NYC.

OKCupid founded and based there as well.

dropbox opened up recently

MongoDB