Apple.com at one point had a nifty effect on their website that would zoom a thumbnail image to a full image. Many people have created JavaScript solutions to imitate this feature.
The problem with existing solutions (see FancyZoom and ReMooz) is that they load the images into the DOM when you click the thumbnail. This results in a slow user experience. They also use graphics for shadows, which causes more loading time for the end user. One of my passions is performance optimization, so this annoyed me.
My solution is MooZoom. I’ve just released version 0.9.1 which contains more options and speed improvements over the initial 0.9 release. See for yourself: I use it on the Projects page for this site.