Bar codes containing any kind of information seem to pop up everywhere these days. They get a big boost from mobile devices which support bar code scanner applications like zxing. The format most commonly used is QR Code.
The future of this idea seems promising (quoting):
For example, Wikipedia displays their QR code on the Wikipedia site. I could also see QR codes as a potential business card replacement. You are at a business meeting, you whip out your mobile and the other party does as well. You "scan" her barcode displayed on the mobile and now you have all of her contact information and not only is it stored in your mobile, but it’s now on your desktop in your contact manager. Imagine the possibilities for dating!A QR Code containing my personal mail address and this blog's URL appear on the sidebar. Also, I have created different versions containing my business contact information. To generate the images I used the QR Code Generator from the ZXing Project.