Concept Board is a german site that is ideal for creating an online interactive "whiteboard". This is a great place to collaborate and not only share ideas but documents and files as well. Also, there are many features that make this an attractive option such as: screen capturing, ease of use on mobile devices etc etc.
I recommend checking out Concept Board by clicking here!!
Thanks to Larry Ferlazzo's review for the tip!!
For a similar site check out Board 800.