QR Codes have come and perhaps gone, but I still find them useful and engaging at times. I learned about using QR codes from @daikinane at uLearn11. Here are the collaborative notes from that year,
I use qrstuff to make my codes, and then use them to link kids to my ncea flashcards, homework assignments, readings, etc. They generally get a kick out of it (though more so if they already have downloaded a reader).
I refer my kids to QRreader at the play store. It's free, and doesn't make an annoying noise every tine they scan a code.
I even use a QR code on my cv these days! They take literally a second to make, and are quick, easy, and fun. Give it a go!