Notebookcast is a free online whiteboard that allows you to share whiteboard space with any devices. You don’t need to install any software, it runs within your browser.
Like any whiteboard software you can draw and add images and shapes. Once you have created a board you can share it with up to 10 users, all of whom can add to the drawing in real-time. This would be good for collaborative work.
The whiteboard is a little basic, and there’s not a lot of features right now – I couldn’t move anything once I’d added it to the page, and I found it often crashed after adding images. But is free and hopefully these bugs will be ironed out soon and more features added.
You can test it out for yourself at www.notebookcast.com