I loved this guerrilla marketing campaign idea from Editoras Online,
view video here. They used QR code stickers to tell a story that pulls information from Twitter. So then I wanted to know about QR codes - heck, I wanted my own code. So I made one up thanks to
http://qrcode.kaywa.com/
If you want to read what it says - you'll need to download reader software to your phone:
http://reader.kaywa.com. If you have an iPhone there are a few free QR code applications.