Augmented Reality (AR) is one of those nebulous computing terms that can mean entirely different things to any two vendors. AR covers everything from games to computer vision to mash-ups of Web services — but the most useful applications are those mobile browsers that grab your current location and overlay relevant information about the things around you. Layar, Google Goggles, and Wikitude, for example, can place photos, Web pages, or a multitude of other information about your surroundings right at your fingertips. But if you care about open source, have no fear: there are plenty of alternatives to the proprietary AR app vendors. Let's look at what they offer, where they differ from proprietary AR, and where the field seems to be going.