I'm not great with genius ideas, but something that helped out people with depression seems obvious and well-targeted. I like the idea of buddying up to help build mini support groups.
I know a lot of people here express low confidence in their skills and difficulty finding jobs, especially in the tech interview portions. Maybe some kind of web app supporting regular (weekly?) discussions about certain tech topics, like SOLID principles, refactoring, TDD, design patterns, etc. Something like a study group/meetup that's relatively language agnostic.
@grant_vinson your message just popped up as I was answering this; what are you thinking as far as a social app for Devpressed?