If the shadows aren't absolutely critical, I'd suggest simply using CSS3's box shadows. They're supported on all recent versions of the major browsers except IE.
-moz-box-shadow: 4px 4px 8px #000;
box-shadow: 4px 4px 8px #000;
About: http://www.css3.info/preview/box-shadow/
The problem with JS-generated shadows (i.e. shadows made with jQuery) is that they're really slow to generate. They're generated pixel-by-pixel, appending the DOM with lots of markup. If you were to regenerate them while the browser's getting resized, it'd eat the user's CPU alive.
If you're brave and want to have resizable shadows no matter what browser the user is using, the other route to go would be using images and CSS to construct the shadows. This method'd be fully resizing-friendly:
http://www.alistapart.com/articles/cssdrop2/