Have you checked out the "jobs" section here on HN? http://news.ycombinator.com/jobs
It's obviously a one-way tool and what you're describing is two-way, but it's a start.
There is something of a talent pool in recommendations between the YC startups. Get involved with one, and you'll probably be able to get more work out of it if you do a good enough job for them to remember it.
YC itself is effectively that. The good people from the startups that fail get picked up by the others. We also run http://workatastartup.org.