Since leaving the current YC batch due to inter-personal issues, I've been working on a (so far) terraforming game in node.js. This is just a super early version, when it's done it will have actual game elements (like AI and collision detection). Check it out and let me know what you think!
Long-term goals for this project are to turn it into a gaming platform where anybody can make their own world and host it, complete with optional micro-transactions and optional subscription fees.
Screenshot: http://imgur.com/Ea9O7 Demo: http://zyu.me/