modalBox.js is a very light weight modal window plugin packed with only most used features and options. Its overall size is around 5.3 kb ( 2.5 kb minified). Core of plugin is completly explained in homepage, so you can easily extend it according to your need.
jQuery plugin for creating stackable modal boxes.
MultiDialog utilizes jQuery UI Dialog Widget for a full featured Modalbox / Lightbox application.
Use the dialog plugin for creating beautiful overlay dialog boxes. You can open multiple dialogs at once, and see all of them awesomely stacked one behind the other giving it a unique look and feel.