Stackoverflow is one of the greatest web applications I've ever seen. It's not just its purpose, but also its quality, design and speed.
Is it just 6 people doing all the hard work? (I don't know if I can call these guys people since they are jedis).
Are you using SCRUM or something like that?
Are you all doing everything or do you have separations like coder, tester, the architecture guy, etc?
And last, what's the hardware running this?