LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
Smoothboard Air - Smoothboard Air is a collaborative interactive whiteboard application for iPads and Android devices that revolutionizes interaction in lecture rooms.
OmniGraffle - OmniGraffle is for creating precise graphics like website wireframes, an electrical system designs, or mapping out software class.
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.
draw.io - Online diagramming application
RealtimeBoard - RealtimeBoard is an online collaboration software created as a team collaboration and online brainstorming tool. It's super easy to use & free!