The same place you meet developers, HN, meetups, conferences if someone says I freelance, use that as your intro to pitch them in a polite manner. I would post every time there is the monthly seeking work thread here on HN.
That site is pretty intriguing, I'm not a member though and I don't think I'd currently qualify for an invite since I don't really have anything to show. Maybe I'll check it out when I can show something I've done. Thanks.