OpenBoard - The OpenBoard software is an interactive white board software.
Scribble Online Whiteboard - Scribble Online Whiteboard is an advanced collaborative whiteboard solution that allows you to draw the sketch using the web-based or mobile platforms such as iPad/iPhone and Android.
Conceptboard - Instant Whiteboards for Teams & Projects
Ryeboard - A practical and visual workspace for modern teams
Scribblar - Scribblar is a free online collaboration tool that is perfect for online tutoring.
Whiteboard Team - Draw, explain and collaborate visually in real-time.