jReject is a simple, light-weight library designed to display a popup based on a the browser, specific browser version, specific platforms, or rendering engine. Provides full customization of the popup.
Uses a small CSS file, and can easily be used on page load or during a specific page event. Also provides a flexible way to beautifully and cleanly display custom browser alternatives in the popup.
jBox is a powerful and flexible jQuery plugin, taking care of all your popup windows, tooltips, notices and more.
jQuery.TosRUs plugin is a great lightbox alternative for scrolling/swiping through any kind of content. On a desktop, tablet or smartphone, inside a HTML element or as a lightbox popup. It's responsive by default.
Pop Easy is a lightweight jQuery plugin that is a must have for any developer to easily create modal windows. Put focus on important elements by applying a mask to your page and opening a customizable pop up modal window.
This is a simple jQuery popup plugin with transition effect.
Smallipop is a customizable jQuery plugin for displaying tooltips.
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).