[malandrew]

With a solid Github and/or StackOverflow reputation. I reckon the former is more valuable than the latter because it results in code being produced as opposed to just discussed.

[Brewer]

That's good, because although I have a StackOverflow account, my reputation is 1. It's a new account. :P

[moonlighter]

I wouldn't bother with a StackOverflow account, at least not in the sense of 'the more I actively participate, the more Karma I build up there". Ditto with HN and GitHub. Posting code there to show off/try to impress just doesn't work and is a waste of time.

Do it only because you WANT to/have fun doing it, otherwise you won't be able to sustain it in the long run anyway.