LightWindow is the most powerful modal window I have seen so far. It has so many features, you have the complete ability to style and position it. It is very easy to implement as well. Lastly, most moal window application didn’t actually test for their media types and how they behaved in other browsers and operating systems. However, LightWindow has done a great job, other than images, inline content, iframe content and ajax content, it also supports Quicktime Movie, SWF and PDF.

Requirements: Any Modern Browsers
Demo: http://stickmanlabs.com/lightwindow/#demos
License: MIT License