Source: Web Whiteboard
Nothing to install, no requirements for the other users. Simply click the Create free whiteboard button and you’re ready to go. To invite collaborators, each whiteboard is given an unique address. This address can be shared with the people that will be collaborating on the whiteboard.
Once you are finished with your masterpiece, the whiteboard can be downloaded as a picture for further use.
Whiteboards are deleted after 21 days if you do not register.