drawonthe.net - Draw on the . net is an online, multi-user, drawing website.

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

skrbl - Simple and easy online multi user whiteboard, start skrbl, give out your URL & start working...

Whiteboard Fox - Simple Online Whiteboard

Wottactic - Whiteboard app for game planning

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.