Lots of tech events in NYC use Meetup (http://meetup.com) -- it's free to join, search, use/attend, but you pay to organize your own.

In addition to Gary's Guide, the nextny mailing list often has announcements, and Charlie O'Donnell sends out a weekly e-mail. Sign up for that one is on his blog.

Also check out thestartupdigest.com the NYC is compiled by Carter Cleveland who started art.sy

Gary's Guide is a good tech events calendar with a lot of startup stuff.