Slack - A messaging app for teams who see through the Earth!
OpenBoard - The OpenBoard software is an interactive white board software.
Smoothboard Air - Smoothboard Air is a collaborative interactive whiteboard application for iPads and Android devices that revolutionizes interaction in lecture rooms.
Conceptboard - Instant Whiteboards for Teams & Projects
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.
Scribblar - Scribblar is a free online collaboration tool that is perfect for online tutoring.