Scriblink - is a free digital whiteboard that users can share online in real-time. Sorta like pen and paper, minus the dead trees, plastic, and the inconvenience of being at the same place at the same time.
Dabbleboard - an online collaboration application that’s centered around the whiteboard. With a new type of drawing interface that's actually easy and fun to use, Dabbleboard gets out of your way and just lets you draw. Finally the whiteboard enters the digital age!
Sketchcast - Sketchcasting allows you to record a sketch with or without voice. Explain something, have fun, or create art.
Imagination Cubed - from GE
Twiddla- "Twiddla calls itself a web-based meeting playground. Not only is it a fun way to swap ideas about a website or image, it’s incredibly useful as well."
CoSketch - CoSketch is a multi-user online whiteboard designed to give you the ability to quickly visualize and share your ideas as images.
WallWisher - the janitor came up with the idea for using a sticky-note/noticeboard interface for communicating on the web.
Corkbaord - an online corkboard for notes
Stixy - Think of Stixy as your online bulletin board. Create as many Stixyboards as you like, one for each project.
Lino It - Online Stikies