Common Sense Education provides a free, downloadable curriculum on Digital Citizenship. Even if you don't teach it directly, it's a helpful read.

GoSoapBox is a system that allows students to respond electronically, in real-time or asynchronously, either spontaneously or to a wide variety of prompts such as quizzes or polls. It is entirely web-based (no app required), but each student needs a connected device (BYOD or 1:1).