If you want to find out more, various people recommended QR Codes at Bath and related pages as a good source of ideas (I certainly found them useful) and I would add Mr Robbo's QR Code posts which have loads of practical ideas and examples.
If you want to find a QR Reader and have a go yourself, Mobile Barcodes lists some of the available applications. (I used i-nigma during the demo but I'm intrigued by Stickybits which @relativism introduced me to). Pick a reader and try it out. I used the Kaywa QR Code Generator to create the codes but there are many other free online tools and applications available.
If you want to contact me for more details, everything you need to know is in this QR Code :-)