P-Loading is a powerful jQuery plugin, for faster and easier web development, which allows you to have a main loading mask platform that is able to use many different spinners by installing P-Loading add-ons.
LoadJS is a tiny async loading library for modern browsers. It has a simple yet powerful dependency management system that lets you fetch files in parallel and execute code after the dependencies have been met.
A tutorial on how to write a CSS3 progress bar and add some cool animation, along with a jQuery counter.
ClassyLoader is a jQuery plugin that lets your add beautiful and animated loaders to your website.
jQuery Fadeloader plugin lets you easily implement a preloader to your site or section, using a cascade fade in effect to show specific blocks of content.
Loadie.js is a lightweight jQuery plugin to create a preloader that doesn't suck.
imageloader is a jQuery plugin for preloading images.
jQuery Waiting is a jQuery plugin to generate spinners and loaders, without images, canvas, or other nonsense. jQuery Waiting uses standard, widely accepted css to style your waiting spinner, and a little jQuery to make it function
What QueryLoader2 does is simply scanning the given elements for images (and background images) and preloading them before the website is visible.
This version has been modified to make it easier for users to implement (especially those who are already into jQuery).