I recently stumbled across this project while browsing the Minecraft forums (hiss! closed source! :P), and I've found it to pretty inspiring. They've already built and open sourced a tractor, brick making machine, various machining tools, an interchangeable "lego like" power source for their modularly designed equipment, at a fraction of the cost of industrial equipment (the prices range from 4 to 40 times cheaper). Their ultimate vision is the creation of self-sufficient resilient communities that can replicate themselves by producing these "village construction kits" and training people in its use, from what I've read, although it has come across as a bit.. fluid
Here is a blog post of theirs where they've used Sauerbraten to render a design they've made, and discuss gaming's usefulness in "making the world a better place", although they don't go into too much detail it's still an interesting subject.
What are your thoughts? Bright shining beacon of the open source way bravely fighting it's way into changing the world in a more direct way? Or a 60's hippie resurgence commune doomed to fail :P ?