Ender-overlay is a highly configurable overlay plugin for Ender. You can easily build your own gallery or other overlay based logic on the top of this plugin. It's just 1.7 KByte (minified and gzipped).
It requires Jeesh and Morpheus for animations. Even though, you can leave Morpheus out if you are fine without animations. Currently it's tested in Chrome, Firefox, Safari, Opera and IE7+. Currently it's in beta state, please report bugs here.
I got a lot inspiration from jQuery Tools, thanks for that.
More information, documentation, demos: http://nemeseri.com/ender-overlay/