I've had some luck using the CSS max-width
You can tell an img tag to max-width: 75% and it will resize the image to fit that much of the available area. It'll even dynamically resize when your stretch your browser window.
Downside: Some browsers *suck* at resize images. IE6 does not support max-width, though pretty much everyone else does on the desktop (haven't tested it with any mobile devices, though).
Josh
On Mar 31, 2010, Lee Passey <lee@novomail.net> wrote:
If anyone has any suggestions as to how to dynamically resize images,
I'm all ears, because this is one of the problems I'm going to need to
resolve for my own co-operative proofing demonstration.