I teach students not to use "weasel words" in their collaborative writing. This includes things like "Many people say" or "it is widely thought" - these statements, unless backed up by a reliable source, lend credibility without fact backing them up. These are words that students should be familiarized with when writing for academic purposes in collaborative writing.
An excellent, useful post from Silvia Tolisano with practice information and graphics about using Twitter in the classroom. This is a must read in edtech classes and in professional development for teachers. Pass it around and learn. In it, she quotes Terry Heick of Edudemic who divided tweets into 3 sections relating to higher order thinking skills: watch, talk, produce. Excellent, useful points about using Twitter in the classroom.
If you want to read how teachers are using digital citizenship in practice, the Flatclassrooms network has lots of great ideas being sharedby teachers like this blog post. One thing we teach the Flat Classroom certified teachers is how to create a CMP (classroom monitoring portal) using Netvibes as depicted here. Digital citizenship should be part of what we all teach.
There are some great things you can do with Google Drive (formerly Google Docs). Here's a lovely post by teacher Helen McConaghy about what she's doing in the classroom with her students and Google Docs. Great ideas.