I strongly believe I could end this tech-letter here and you would still get the message. But who am I if not someone who explains way more than required?
If you were looking for a very simple, straightforward, what-you-see-is-what-you-get (WYSIWYG) tool that also lets you collaborate in real time with other users and also lets you share your creativity... first of all, that's way too specific so relax; but second of all, this one's for you.
Witeboard is exactly what the name suggests-- a whiteboard (or blackboard, depending on the mode you select). This online tool lets you collaborate with others instantly, without sign up required. You get to cross-platform collaborate, which is short for "You can use this on every device you own, simultaneously"; i.e. on your phone, while someone else is on their laptop, while someone else is on their tablet. All you really need is a browser.