Vanilla JavaScript Plugin

Uglipop.js  

An ultra lightweight 2 kb non-fancy, yet highly customizable, modal popup window.

Plugin Website  Demo

Related plugins

PicoModal  

A tiny modal window plugin with a useful set of options.

Tingle  

A lightweight, yet powerful modal window plugin with lots of great features.

Notifier  

Notifier is a tiny plugin for displaying Growl-like popup messages.