There are two types of simple augmented reality: marker-based which uses cameras and visual cues, and markerless which use positional data such as a mobile's GPS and compass. (Johnson et al, 2010)
And Markerless AR:
Even beyond the fun, the games, the learning, and medicine...
Rolf Hainich in his book The End of Hardware (2009) sees this technology as something that will also benefit the environment by replacing hardware with small virtual devices. Educational games that use markerless AR require only one handheld device for a group of students working together; virtual games required each student to have his/her own individual computer. "Virtual devices could definitely save a lot of natural resources...dumping a 20g vision simulator is not as bad as dumping a 20kg monitor." (Hainich, 2009)
Hainich, Rolf. (2009). The End of hardware, 3rd edition. Booksurge.
Maker-based AR
Creating your own marker-based AR was once only done by programmers who could write the complicated code necessary to create the holographic illusions, but it is getting easier everyday for the common individual to create their own. Web sites that provide code, or applications are springing up everyday. One example is Artookit. Why might you want to do that (I mean aside from it just being fun and cool) think about a business card or a resume that uses the technology to showcase a creation. Currently the cards appear more gimmick like than anything else, but "just because it looks goofy now, doesn't mean the technology won't hit its stride." (Stewart, 2009)
And not all of it is goofy. For example the GE ad on the left, and the ways architects are using this technology to showcase designs they've built in Sketchup.
But you don't need to create your own AR to experience it. It's as easy as printing a marker developed by someone else, then holding it up in front of a web cam. The GE images on the left use a Flash-based application to access your web cam and display the "fancy" image you see, but many of these marker-based experiences don't even need to do that.
You can find some to try yourself. Here is a marker from http://blog.craigkapp.com/?cat=15. Click on the image to get the pdf to print.
Stewart, A. (2009, November 16). Augmented reality busiiness cards. Retrieved from http://www.hotcards.com/blog/1/444.html