It’s been a long time between posts and this is the main reason.
Google Plus combines many of the best features of Facebook and Twitter and has become my favourite way to learn from and share with others engaged in education and technology. Unfortunately Google has restricted G+ to those aged 18+, but in the future it may be rolled into Google Apps for Education making it available to both primary and secondary students.
I highly recommend Google Plus for those aged 18+.
Update: 28/10/11. Google Plus has just been incorporated into Google Apps for Education. Unfortunately the 18+ restriction still applies.
Update: 26/01/12. As of 26 Jan 2012 Google Plus is available to users aged 13+.