GE has created a wonderful online whiteboard.
Besides the fact they have included the ability to invite other to collaborate with you (and chat in a small side window), they have included many options - to name a few: stamps, shapes, lines and text. You can change the color and somethings have a size option. You can undo your own work. You can print, save, email and even replay what you drew. Great for all ages. Have fun!
http://www.imagination3.com/LaunchPage