QR Codes work like barcodes that webcams and mobile phone cameras recognise. They read the code and take the user to a website within a few clicks.
QuickMark is a software that I have used with webcams. When QuickMark recognises a QR Code, it displays the URL and users double click the link to open the website.
At my school, children in Key Stage 2 have been successfully accessing the internet using QR Codes. Instead of taking the device to the QR Code, Tom Barrett reversed this and let children take the QR Code to the device that read them; in his case a NetBook or laptop.