QR codes are increasingly ubiquitous on ads as quick links to sites-at-a-glance. If your students have phones then they probably have a QR (quick response) code reader. Try these codes for fun. They link to important language sites.
If you don't have a QR reader, here is where you can get one for your phone:
IOS: App Store, search: QRafter (It's the one I use and recommend)
Android: Marketplace, search: QRafter.
I can't recommend others because I've tried many which don't reliably read all QR codes.
Try these! Launch your app and let your camera hover over these squares and you should get a link.