I just discovered swfIR image replacement, which uses Flash and some fancy javascript to replace your standard images with enhanced images that can feature rounded corners, drop-shadows and the like.
swfIR (swf Image Replacement) is here to solve some of the design limitations of the standard HTML image and its widely-accepted associated CSS values, while still supporting standards-based design concepts. Using the dark arts of JavaScript and Flash, swfIR gives you the ability to apply an assortment of visual effects to any or all images on your website. Through progressive enhancement, it looks through your page and can easily add some new flavor to standard image styling.
As Mike Davidson points out, the concept of using flash for images is sure to upset some standardistas somewhat, but there are definitely cases where this technique would be invaluable, especially with liquid layouts. It also adds another level of design flexibility, which is not a bad thing at all.
swfIR: swf Image Replacement