One of the best resources is Common Sense Media. It includes resources sorted by grade or by theme. They have videos and downloadable (PDF) lessons. There are also eight iBooks for use on iPads or other Apple devices.
Media Smarts is another good site for digital citizenship classroom resources and lesson plans. There are Alberta-specific resources for all grades, and a set of videos and lesson plans related to media literacy.
As well, check out the NHL's Future Goals Program.
The main thing is to have these discussions.