OpenBoard - The OpenBoard software is an interactive white board software.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Conceptboard - Instant Whiteboards for Teams & Projects
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Scribblar - Scribblar is a free online collaboration tool that is perfect for online tutoring.
Slack - A messaging app for teams who see through the Earth!