There's also the Hacker News Chatterous chatroom, which has 119 members, including a number of founders from the Y Combinator Winter '08 cycle.

You can hook your Jabber/GTalk, Email, Phone contacts into it as well.

One-click invite link: http://www.chatterous.com/landing/hnyc/hcker/

by phone: text CHTR JOIN hnyc hcker to 41411

by email: @join hcker in body to hnyc@chatterous.com

by jabber/google talk: add hnyc@chatterous.com and send @join hcker