Slack - A messaging app for teams who see through the Earth!
Padlet - Visual boards for organizing anything.
Smoothboard Air - Smoothboard Air is a collaborative interactive whiteboard application for iPads and Android devices that revolutionizes interaction in lecture rooms.
BookWidgets - BookWidgets is an excellent application that let you create engaging exercises in minutes and easily share a varied variety of beautiful and fun activities with your classroom and others.
Groupboard - Free collaborative online whiteboard, web conferencing and online tutoring software that can be embedded in your own website. Used by many online tutors, schools and universities.
Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.