Stack Overflow is a collaboratively edited question and answer site for programmers — regardless of platform or language. It’s 100% free, no registration required.
I’ve thoroughly vetted Stack Overflow — the podcast, blog, team, and the question and answer main site.
Here is the “46th episode of the StackOverflow podcast, live from MIX09, where Joel and Jeff answer questions from the live audience.”
I’m giving this effort a recommendation without any reservations. They have some interesting variations on voting and reputation and a very different approach to how your un-vetted opinions affect the site. They are committed to preventing any gaming of the voting system.