http://drawball.com/

a site where there is this massive canvas on which you can leave your own mark. the thing is so huge that the maximum area you can cover with the ink given to you is about 2 pixels from the perspective showing the whole circle. (for some reason it didn't appear to work on me as I just tried it.. seems to have something to do with the aprilfools and the whole canvas being turned a little over 90 degrees.. but you can still at least look at this drawball history playback at here where you can see 40 hours of life on the canvas in one second)