Augmented Reality (AR) is pure science-fiction, the idea of overlaying an informational world on top of the physical where you could create entirely artificial structures, central hubs of communal hardware hallucination offering everything from imaginary artworks to real world opening hours. And in a wonderful parallel with itself, this fictional story actually is leaking into reality with Google Goggles.
Goggles isn't the only AR application, but it's the most exciting simply because of the search engine. By design any AR system must have the ability to detect the world and locate itself within it, otherwise known as "a camera" and "GPS", other-otherwise known as a modern phone. An application able to connect these tools together with Google search, other^3-wise known as "access to an entire informational world we've already built" and your phone becomes a window: a viewport into all the information that exists for any location.
The best bit is, little things like always knowing where you are and being able to learn about anything you see are only the beginning. The internet was originally the ability to exchange text messages, and it's grown in ways that were absolutely impossible in any previous media. With modern mobiles meaning that AR-access would be standardized and mass-market - meaning every electronic tribe would put it to their own purposes. Invisible electronic graffiti tagging an entirely different world depending on how you want to look at it: whether you paint a pleasant Parkour route or tag security cameras is up to you.
Even that is amateur hour, because we were able to think of it ahead of time. AR isn't "another phone gadget" or "another type of map," although it involves both of those. It's an entire imagined world on top of our own, one you can edit and share with others. We're only limited by our imaginations and our graphics hardware, and the latter's no limit at all.