Wikipedia has a good entry on Quick Response (QR) codes.
OK, your smart phone or iPad has the ability to scan QR codes? You can add me and this Blog to your Contact list by scanning the first image, and add some text information by scanning the second.
These QR codes were generated free at http://www.itmt.co/QR/
You are already seeing these QR codes appearing in magazines and billboards. I plan to put one on my business card. Anyone with a QR-code reader on their photo device can scan the code and go to a specified website, send an email to a specified address, and/or add name, phone, and address information to their Contact list.