Same problem in Boston. The recent HackerNews meetup was great, but I found it hard to stay connected with the people I met through reddit. Strangely, I don't have a desire to go to a lot of the Meetup.com groups..
The problem I've noticed is the lack of re-engagement after initially meeting people face-to-face.
There are sites like letslunch but many 1) don't have the luxury to do >=1 hour lunch or 2) don't work in the city