Here's another useful tool but an online one. Dabbleboard, www.dabbleboard.com is a whiteboard tool and offers many useful options, some real good ones as well. It takes the concept of a board further by introducing options like intuitive shape guessing, inserting images, pdf documents, etc. It offers a good number of toolbar options to help the user do things like freehand drawing, colouring, and much more.
The tool works on the philosophy of "share-chat-collaborate" and leaves it to the discretion of the user whether to share the drawings or not.
With a number of created drawings available, the user can definitely judge what this tool can do. So, don't forget to view the 'Drawings' section.