Here is a useful scheduling tool, I would imagine its best use to be to organize meeting times between teachers and students. Everyone can access the same schedule without the need to synchronize or coordinate multiple calendars.

Google Hangouts, in spite of an rather unprofessional sounding name, is a fantastic way to have live interaction with students, or even just between students. A Hangout can be set up and left active, participants can drop in and out as they wish. There are even apps for mobile devices now. A great tool.
https://plus.google.com/hangouts

A short article listing 4 benefits of using smartphones in the classroom. While I'm still not totally convinced, some good points are made here. The issue I don't ever seem to see addressed in articles like this, though, is how to keep students from going to facebook or their texts after using the phone for a learning purpose.