Scribblar reminds me of Blackboard or Moodle for online classes or collaboration. But you don't always have access to either of those if you aren't part of a university or organization that uses those tools. Google Docs has a great collaboration tool, as well. But, if you want a quick & easy way to collaborate right away, Scibblar can do that.
Here's what the whiteboard looks like. You can add pictures, screen captures and other items. You can type, highlight, draw, chat, use the audio to speak...etc.
It can be used for brainstorming, demos, tutoring, interviews, tests and so many other ideas.
If you click on the screenshot, you will get a better view.
Or you can simply go there & start right away.
It's all FREE. You can check it out here.