SimpleModal is a free jQuery plugin to create lightweight & beautiful modal dialog. SimpleModal gives you the flexibility to build whatever you can envision.
Very basic & unstyled modal dialogs are provided as examples but they can be styled through external CSS or through properties in the options object.
In addition, SimpleModal dynamically centers the modal dialog, unless the position option is used, which takes precedence.
Website: http://www.ericmmartin.com/projects/simplemodal
Demo: http://www.ericmmartin.com/projects/simplemodal-demos/
Download: http://code.google.com/p/simplemodal/downloads/list