Boxer is a quick and simple way to display images, inline-content or iFramed URLs in a lightbox-style modal.
The jQuery BlockUI Plugin lets you simulate synchronous behavior when using AJAX, without locking the browser. When activated, it will prevent user activity with the page (or part of the page) until it is deactivated.
BlockUI adds elements to the DOM to give it both the appearance and behavior of blocking user interaction.
Simple Modal is a small plugin to create modal windows. It can be used to generate alert or confirm messages with few lines of code.
Simple Modal is not a lightbox although the possibility to hide parts of its layout may partially make it similar.
jQuery.fluxoModal is a jQuery plug-in similar to lightbox. It can highlight any kind of html element inside an html modal window, blurring the background using html5 canvas, CSS3 animations and a crossbrowser fallback for IE.
Avgrund is a jQuery plugin for modal boxes and popups. It uses interesting concept showing depth between popup and page. It works in all modern browsers and gracefully degrade in those that do not support CSS transitions and transformations (e.g. in IE 6-9 has standard behavior).
An alert alternative for jQuery that looks good. Apprise is a very simple, fast, attractive, and unobtrusive way to communicate with your users. Also, this gives you complete control over style, content, position, and functionality.
Reveal is a jQuery plugin for dead simple modals that comes with some sexy base CSS and can be implemented programatically or with the new HTML5 custom data attributes (data-attribute).
Display text, html content, images and ajax requests with 5KB code.
noty is a jQuery plugin that makes it easy to create alert, success, error and confirmation messages as an alternative the standard alert dialog. The notifications can be positioned at the top, topCenter (like GMail), bottom, centre, top left or top right. There are lots of other options in the API to customise the text, animation, speed, buttons and much more.