What is a QR Code?
A QR code is a code that can be scanned by smartphones and portable devices that directs the user to more information such as a website, video, image or information.
How could I use QR codes educationally?
QR Code Creators
http://www.qrstuff.com/ (my personal favorite)
A Ready to Use Example
Printable Periodic Tables with Codes
http://www.flickr.com/photos/periodicvideos/5915143448/ (with Element symbols)
http://www.webelements.com/nexus/chemistry/printable-periodic-table-qr-coded (without symbols)