Magnific Popup is a lightbox plugin with emphasized features for responsiveness.

Magnific Popup integrates with Zepto.js as well. It’s focused on performance and on providing the best user experience possible.

You should give Magnific Popup a go because it’s heavily optimized, supports Retina displays and is highly extendable. Browser support is also good, although expect some bugs with IE7.

iLightBox is a plugin for creating an all-encompassing and feature-rich lightbox.

Among the notable features are:

• Fullscreen, retina-ready skins;
• Swipe event support;
• Supports most devices and browsers (down to IE7);
• Comes with a powerful JavaScript API;
• Keyboard events et al.

You can tweak the plugin like mad and use basically any content you can imagine in the lightboxes. What’s more, it also recognizes video not only from YT/Vimeo, but also from Hulu, MetaCafe, Dailymotion and other websites.

fancyBox is a jQuery library for zooming images and multi-media.

It’s extendable using helpers, responds to screen size changes, and has integrated slideshow functionality.

fancyBox also comes with image transitions, although I couldn’t find an example for those, and uses CSS3 for rounded corners and all that good jazz.

A WordPress plugin should be released soon, too.

Avgrund is a modal UI library for making dialogues with a neat “depth” effect.

Avgrund, Swedish for ‘abyss’, isn’t really meant for practical use, but rather for toying around with CSS transforms and filters.

Whatever the reasoning behind this plugin, it works really well and offers a fresh way of creating modal dialogues. 

FrameWarp is a plugin for showing separate pages in a LightBox-like environment.

It is released as a tutorial, explaining the whys and hows of making such a plugin.

Although FrameWarp is basically a LightBox plugin, it still has interesting features like a JavaScript fallback and a cache system for subsequent loads.

FrameWarp is a neater way of loading separate pages than a LightBox.

Lightview is a jQuery plugin for creating overlay windows (lightboxes).

It features an easy-to-use API and extra media support which is sometimes lacking in other LightBox plugins.

What’s interesting about Lightview is how comprehensive the library is.

It features a powerful API, skinning, callbacks, and has more options than a regular user would need… ever.

Lightview is quite the heavyweight in terms of size, too: ~130kb for all required files.

The license is free for non-commercial use, and licensing for commercial projects starts from 50EUR.