I created a HTML 5 based animation critiquing tool for the Ember team today. It uses Multiuser Drawing Pad Built with Pure JavaScript/HTML5/Canvas from http://www.unionplatform.com in combination with some scripting tutorials I found (including http://www.html5canvastutorials.com/advanced/html5-clear-canvas/).
This tool is incorporated with the Ember bible site I created to help organize the production and increase the pipeline flow. I combined the drawing technique and layered an embedded Quicktime element behind the HTML 5 canvas.