A few teachers have asked me recently to explain QR codes. Nobody can explain things as good as Lee LeFever at Common Craft, so I recommending watching his video; it is just over two minutes in length.
Then start to think about the implications for a classroom teacher. This post on the Teaching Happily Ever After blog may give you some ideas as well as provide some how-to information.
Try it out! Here’s a QR code I just generated in about 10 seconds on my computer using Kaywa QR Code Generator. You’ll need a QR code reader on your smart phone. Go to the “Market” or “App Store” to find a free one to use. I use an app called QR Droid on my phone, but there are lots of other options.