Check out Dabbleboard

If you’re looking for a practical way to share online those draft flow charts, preliminary diagrams and rough sketches of data structures that you might usually just scribble down on some random piece of paper, skip the pen and paper phase next time and take a peek at Dabbleboard. It will most likely save you a scan and having to decipher whatever hieroglyphs you scribbled down diagonally on the back of some specs.