CSS works for things like this as well, but I don’t usually use CSS for rollovers when there’s a potentially unlimited number of images to swap out. You could, but it would mean that you’d probably want to add CSS code to the head dynamically to set your swap classes to the images on that particular page (since you wouldn’t want to have to add them all to your stylesheet). The other disadvantage to most CSS techniques is that they generally use background images, which don’t show up by default when printed from most browsers (we once had complaints about this that forced us to rewrite the entire script).
CSS is perfect for navigational rollovers and other elements that don’t change from page-to-page, however.
@overhaulmedia: If you’re still offering that reward, why don’t you make it a donation to the MODx project instead:
http://modxcms.com/donate.html
No pressure, of course...