The square squiggly box in the "Upcoming Events" column on the left of this page is a QR Code that can be included in emails, and on printed posters etc. to give mobile and tablet users a quick link to the relevant website.
The ideal use would be in printed marketing materials for businesses, and the like.
Simply include the box in your printed materials and users who point their smartphone cameras at it will go through to your website. For example the QR code on the right is for Brian Cox's website listing "Wilcannia Auto Repairs", listed in the business and services directory of this website.
For Android phone users you can download and install a free app (such as "QR Droid"). Once installed and opened, simply point it at the squiggly box, and voilà.