FlockDraw

FlockDraw is a collaboration drawing tool.  Basically, you create a flockdraw site, share it with others, and you can all draw at the same time.  It's quick and easy...to get started, simply click the Start Drawing button. Enter your name under Flockdraw, click Join, and you are on the page.  To share it with others, simply copy and paste the website address and send it to friends.  Teachers, you can post the link on your webpage to make it easy for students to access.
The tools are on the right hand side...basic drawing tools...not too difficult to figure out. There is also a text tool to add text.
These can also be embedded into your blog or another site (see below).
Note:  I am having some trouble figuring out how to get it to save for others to draw on it after you have closed it out.  If you figure that out, I'd love to know.  In the meantime, as long as you don't close the window, seems like it is ok.

If you have used this with students, please leave a comment to share with those reading (and me, too!)

Here is a sample I quickly made.  Please feel free to add to it so you (and others) can see what it does.