I've been enamored with the idea of QR codes lately. Over at LabSpaces, I mentioned that I'd like to include them on my next round of business cards.
I've found two applications which have proven useful in my quest to QR code things.
The first is a web app by Kaywa. If you give them a URL, they will generate a QR code image for you which you can then download and do anything you want with.
The second is ScanLife, which produces an app that I have for the BlackBerry. It takes some getting used to, but if you hold your camera back far enough (I'd say at least 6 to 10 inches) it'll actually work fairly well. There are also applications for the desktop where you use a webcam as a barcode reader.