We're working on something similar, but to match developers up with scientific, conservation and charitable projects that need help. I'm not interested in hijacking this thread, but if anyone wants to be kept informed, my email is in my profile.
We've found over the years that having one specific task for new contributors to complete makes a huge difference in attracting that next contributor. See http://mairin.wordpress.com/2010/07/23/second-fedora-design-... for a really successful effort along those lines.
If you want to join #openhatch or join http://lists.openhatch.org/mailman/listinfo/events/ and chat with us, we'd be happy to see if there are ways we can both learn from each other!
We've had similar feedback about specific tasks from the very few people we've shown the site to so far, and hearing it from you hammers it home.
At the moment we're at the stage of recruiting initial projects. We'd love to talk to you guys, and will drop along to the IRC room :).
A very reasonable thing would be to think about the various ways people are learning open source-related skills, and make a badge site, and then make sure the places where learning happens also participate in badge publication.
If that interests any reader of this comment, we'd love to hear about it! Joinhttp://lists.openhatch.org/devel and say so.