Another free tool to make slideshows--just add images, attribution and comment..will play just like other Web 2.0 tool slide shows and can be embedded on social media or lms (learning management system). Played around with it and it's quite easy.
Edumodo has lots of potential for teachers and students; you can control who is part of the group and you can monitor, two important considerations with social media and students.
You can set up online meetings with Ohours--open office hours. I see lots of potential here for online meetings.
You can also meet other people, which doesn't seem to me to be terribly helpful...whatever.