The QR codes are sort of barcodes that can hold thousands of alphanumeric characters of information, and their ease of use makes them practical for businesses. When you scan or read a QR code with your iPhone, Android or other camera-enabled Smartphone, you can link to digital content on the web; activate a number of phone functions including email, IM and SMS; and connect the mobile device to a web browser!
Cool! So my quick search revealed there are many free QR Code generators such as Kaywa and others, and naturally I immediately filled in my The Travel Photographer website's URL, and voila!!! The square barcode you see above is the QR Code for it. You scan it with your iPhone/Android and your browser will immediately log on to my website.
This is the QR of for my blog, The Travel Photographer's Blog:
And finally, here's the QR Code for The Leica File:
Is it useful for photographers? I have no idea. For the time being, I can only think of one use for it (apart from how the airlines and banks do), and that is to have it printed on one's business card. The recipient would scan it into his/her device and would be immediately logged on to your website.