The above is an example of QR Code: a kind of two-dimensional barcode that can be used to encode any sort of textual data. As cameraphones and smartphones become more common in North America, you may see more and more of these. They are already common in Japan. Nokia has a website that lets you make your own mobile codes. You can make a simple business card like this:
URLs, phone numbers, and other sorts of information can be similarly encoded.