QR codes are a great and easy way to share digital materials and resources within your classroom. I use it in 2 different ways.
1. From the teacher to the students:
Since I have my assignment sheet as a live Google Document, I created a QR code and then printed them as stickers that students can easily put in their agenda or notebook. It is very convenient and fairly easy to do (scroll down to see a video tutorial on how to do it). The advantage of such a system is: no need to print your assignment sheet anymore! The student just needs a phone or a tablet to scan the code and voila! They know the homework for tonight! (it won’t prevent them from making up excuses for not doing it though 
See Also: Why You Should Start Using QR Codes In Your Classroom
I also use QR codes when I want to quickly share a video I created using Explain Everything or an online assessment created by Google Forms. I print the QR code, put it under the doc cam and voila! The entire class can easily scan the code to access the video without having to navigate to a website or check their emails. On the bonus side, when a student is absent, I keep the QR code for her/him. So the next day, they can still view the video tutorial I created by simple scanning the code.
2. From students to students:
Using the QR code feature, my students created ‘mural portfolios’ where they can easily share and make available to the entire class their work for review and comment. For example (see picture below), a student created two index cards with two different projects she did this year (an infomercial and a TV show). What I found with this way of sharing, the students are more engaged by scanning and reviewing individually their classmates’ work, often providing insightful comments rather than just watching the projects as an entire class.
I have in my classroom a wall of QR-Portfolios with each student assigned a dedicated space where she/he can store the various index cards and projects they create. The nice feature of such a system, it makes it easy for any of my students to share their work, and any type of file would work. You do not have to worry about embedding codes into an e-portfolio platform.
Example of a QR portfolio:
