Forget about Facebook for a moment, what's the best way to build community online?

I have a community of startups/entrepreneurs, mentors, and investors I want to connect in an engaging way: give them updates, job board, events calendar, discussion boards. Google groups used to, sorta be a way of doing this. And I know there are a ton of white label social networking apps. Anything anyone’s used recently that’s particularly well designed, usable, and useful?