Since I've gotten my Droid, I've been happily clicking at QR codes. It's like magic. My camera sees it, and I get taken to a web page, or download a program, or whatever. After reading an article about how writers could be using QR codes by Sierra Godfrey, I'm totally going to be spending some time creating my own QR code.
For more information about QR codes, what they are, what you can do with them, and how to make one, please check out Sierra Godfrey's post "QR Codes for Writers".