Just sharing a new bit of free open source microblogging software that's recently been released. It's an alternative to Facebook, Twitter, Google+, etc. that keeps your teachers' and learners' privacy safe and secure, i.e. since it's running on your own server, no-one but you has access to the database so Facebook, Twitter, Google, et al can't access it to harvest users' data.
If you haven't already read it, I co-authored an article on the issue: http://blog.matbury.com/2011/12/11/a-thorny-issue-protecting-teache...
The microblogging software's called StatusNet and you can find out more about it at http://status.net One of the biggest advantages of open source microblogging is that we have the option to allow other microblog sites, e.g. from another school, to collaborate and microblog between schools and organisations, while still maintaining users' privacy and security via the OStatus protocol.
I've put up a quick demo of it on my server: http://statusnet.matbury.com/index.php and you're welcome to have a look and even sign up and try it out, i.e. post some silly messages under a pseudonym. In a realistic situation, registration would be locked down so only admins could create accounts, usually by uploading exports of learner databases (the standard way to bulk-create user accounts).
P.S. I promise not to sell your personal data to Facebook, Twitter or Google! ;)