JQuery dRawr is a jquery plugin to turn any canvas element into a drawing area with a lot of useful tools and brushes.
Screenshot:
Usage:
<div style="width:350px;height:300px;" class="some-container">
<canvas id="canvas"></canvas>
</div>
$("#canvas").drawr({ "enable_tranparency" : true, "canvas_width" : 800, "canvas_height" : 800 });
$("#canvas").drawr("start");