Witeboard - A real-time whiteboard for your team. No signups required.

Ziteboard - Ziteboard is an zoomable online whiteboard that lets team to collaborate in real-time.

Whiteboard Fox - Simple Online Whiteboard

Voynetch - Share your visual notes and graphic recordings.

Stormboard - Stormboard empowers data-driven companies to turn their unstructured whiteboards into data-rich collaborative workspaces; enabling data-driven decisions and efficient processes — often eliminating the need for meetings entirely.

AuthorBee - Organize Twitter around your interests