Edmodo and Common Sense Media have partnered to create a digital citizenship starter kit. This seven page PDF contains a three part lesson on digital citizenship. At the completion of the lesson you can have your students take and sign the digital citizenship. The pledge highlights some of the key parts of being a responsible digital citizen. You can see the pledge sheet below.

Applications for Education
You can download the digital citizenship starter kit from this Edmodo page without registering or signing into Edmodo. Even though the kit clearly has a secondary purpose of getting teachers and students to sign-up for Edmodo, it is still a nice little resource for an introductory lesson on digital citizenship.