OpenBoard - The OpenBoard software is an interactive white board software.
Xmind - Xmind is a brainstorming and mind mapping application.
Conceptboard - Instant Whiteboards for Teams & Projects
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Scribblar - Scribblar is a free online collaboration tool that is perfect for online tutoring.
MindManager - With MindManager, flexible mind maps promote freeform thinking and quick organization of ideas, so creativity and productivity can live in harmony.