[sdfjkl]

Quick & dirty hour marks:

  --- pixelclock.html.orig	2011-12-06 16:40:56.000000000 +0000
  +++ pixelclock.html	2011-12-06 16:39:43.000000000 +0000
  @@ -23,6 +23,7 @@
           var inpos = (y*width*4);
           for (var x = 0; x < width; x++) {
               var color = (y*width)+x < elapsed ? low : high;
  +            if (y % (3600/width)) { color = (color+128)/2; }
               imageData.data[inpos++] = r;
               imageData.data[inpos++] = g;
               imageData.data[inpos++] = b;

[sdfjkl]

With hour stripes, labels and adjustable width (see source).

http://dl.dropbox.com/u/136288/pixelclock.html