I have spent a bit of time this afternoon looking into QR codes, and how they can be customised to incorporate logos or other information. I think the first I saw of this trend was a BBC logo embedded into a QR code, but numerous people have tried it out, such as these ones from Japan, where the QR code has already been used much more widely than in the UK.
If you haven't come across QR codes before, they are much like barcodes, but have the ability to store much more information in them. Perhaps the most common use is to store a website address in them. When scanned with a mobile app like Bakodo or the Google app for the iPhone, the handset can load up the website it points to, and instantly give the user more information about the tag they have scanned.
These 2-dimensional barcodes have a tolerance for errors, meaning that bits of it can be missing or covered up, while still being able to be read and used. That's quite handy, if you want to make them look a little more interesting and include a logo or something to attract people's attention to them. Even better, it's as simple as generating a normal QR code from the Google Charts API (e.g. one for dankarran.com), downloading it, opening it in your favourite graphics editor, and inserting your logo. Check to make sure your scanner can still read it, tweak it if necessary, and you're set. Set the error correction level to the highest value possible (chld=H in the chart URL) and keep your URL as short as possible to give you most flexibility around your logo and less chance of it breaking barcode scanning applications.
Using QR codes to improve location-based information
QR codes could be quite useful for tourist information signs, to give people quick access to more information about the local area, a map of local amenities, or directions to whatever they are looking for. Most phones that have the ability to recognise a QR code probably also have a GPS or some other form of positioning built in, which could help them find their location on the standard Google Maps, but doesn't necessarily help them get at other detailed information, perhaps provided by the likes of OpenStreetMap or provided by local information sites or the local government. Using these codes to point to targeted local information could be of great use to visitors (as long as there's a note to tell them how to make use of the QR code).
A QR code like the one at the top of the post could be useful for someone standing at a tourist information point in the Sea Terminal in Douglas, Isle of Man, as it takes them to a map centred on that point. The site it points to doesn't do much more than providing maps of the Isle of Man at the moment, and doesn't work too well on a mobile yet, but could (and hopefully will, before too long) provide much more information that could be of use to visitors. Similarly, the one to the right points to a map of Douglas on the OpenStreetMap site.
I haven't seen many QR codes in use yet, but hopefully they could become much more widespread in coming years. Could you see yourself making use of codes you found out on the street?