Today, I tested a few new things from HTML5, I have to say this, they are just pure awesome.

http://doodlefun.x10.bz/

Some improvement:
-discard circle drawing for now, use path and stroke.
-change line style to round.

Yet to come:
-Simple UI to change line width and color.
-Better circle drawing.(Idea is there, technical problem)
-Fun background.