I don't know if it's deployed yet but Jason Roberts of techzing (Great Podcast btw, here: http://techzinglive.com/ ) has been talking about a node.js rewrite of the backend for car hire service Uber (http://www.uber.com/)
(ASIDE) Really appreciate the heads up on techzing -- been looking for a podcast to add to Java Posse and Mixergy for over a year and never been happy with Podcast discovery in iTunes. Just added TechZ and can't stop hitting "GET" reading through all the past episodes.