1- Draw It Live
Draw it Live is a free application that allows you to work together with other people to draw in real time. You simply create a whiteboard and share its URL to allow other people to join in.No password is required, and no special plugins are required.
Flockdraw is a free to use online whiteboard based painting & drawing tool. It makes it easy to draw online free with multiple people for fun or business. You can have unlimited people in a room and the drawing updates in real time. Uses different colors, shapes and text
3- Sketch Lot
A web whiteboard for schools. Create a sketch, share it with students. They mark up their own and share it back. No plugin, installation or app required! Works on all modern computers, smartphones and tablets! No Student sign up! Teachers add students to their account.
4- Realtime Board
RealtimeBoard is an endless online whiteboard where you can upload images, draw, add text, post notes and comments and save the results instantly. It is a great web tool for collaborative work as it allows users to invite people and start collaborating.