The technology of QRcodes is being hyped for advertising and marketing , (and making money for telstra). Yet it has wide application, there is a Mobile Barcode Add On for firefox, that lets you get a QRcode on the fly on your screen from any website you visit. Also google has a neat QR code generator, part of google chart api, that lets a developer generate the code from within the HTML on a webpage. There are also plenty of standalone applets such as barshow. The use of the codes are definitely not limited to the web. Infact it is better if they are on physical objects, not just billboard. They can even be merged with photos and still work (as above).
You don't even have to use them for connection to a web, they could just be a copyright notice that you embedded in your photos as a graphic watermark. You might need to experiment with this because the code will need to be large enough to be readable, but small enough to not be obtrusive.
If japan is anything to go on the biggest applications might be for self promotion, of blogs and as a trendy but very personnel fashion statement. There are a any number of free web sites that can help you create your own codes. My favourite, at the moment, is Nokia (by default it creates a datamatrix code, so you will need to change the code to QR code towards the bottom on the leftside of the screen). Here a few of the better ones Nigma, Kaywa(has options for generating different sized codes), Lunaqr (which includes Vcards), Viooli (which can generates coloured codes), Moji-Q (really neat coloured codes as gif image with a translucent background), Winksite, Snapmaze (has the added bonus of being able to automatically generate your code on a custom t-shirt from zazzle), neoreader (which can reader a variety of codes, but the site only generate datamatrix codes) and finally billed as the cutest generator on the net xns.co.js which uses and army of little "code bots" to build the code while you watch (instructions are in Japanese but I'm sure you can work it out)