A VoiceThread is a collaborative, multimedia slide show that holds images, documents, and videos and allows people to navigate slides and leave comments in 5 ways - using voice (with a mic or telephone), text, audio file, or video (via a webcam).
This app works with Dropbox to allow others to send you files without seeing the contents of your Dropbox. Useful for collecting assignments from students.
"Google+ / Google Hangouts: Google+ can be used similarly to Facebook, but using circles can address some of the privacy issues potentially raised with Facebook. While neither of us uses Google+ extensively in our teaching, Google Hangouts have proven invaluable for synchronous engagement. The drawback of Hangouts being limited to 10 simultaneous video feeds can be addressed by having groups of learners (with or without a teacher) act as a roundtable with a backchannel on Twitter or in the chat box inside the Hangout."