I'm looking forward to the open source fest! Unfortunately, I won't have anything to show, but I'm hoping to get involved with something.
Maybe one thing you could do is provide a way for the open source project teams to post where they need help. Kind of an open source job board. It might be especially beneficial at MIX because there is a higher concentration of us UX/Front-End people and many open source projects tend to be weak on the design and UX side of things.