Augmented reality. It's definitely a buzz phrase, but what is it, exactly? How do you experience it? Is there an app for it? Oh, most definitely. Here are 10.

True to their title, augmented reality apps add something to what you see, using a combination of camera, GPS, and sometimes, in the case of the iPhone 3GS, a compass. The result is something like a real-life heads-up display on your phone, and it's spectacular.

It's been a few months since Apple enabled AR apps in the iPhone's firmware, and as you might expect, there's been an explosion of new takes on the concept. Here are ten of the best:

Note: Most of these apps will work best with the iPhone 3GS, and some explicitly require it. It's worth checking into exactly what you lose without the compass before downloading. Also, here's the article in one page.