Query Loader2
Version of the QueryLoader by Gaya Design. Preload images with ease.
Blazy
bLazy is a lightweight lazy loading and multi-serving image script. It's written in JavaScript why it doesn't have any dependencies for 3rd party libraries like jQuery. bLazy is working in all modern browser including IE7+.
RequireJS
A file and module loader for JavaScript
jQuery Pjax
pushState + ajax = pjax
Nanobar
Very lightweight progress bars. No jQuery
Webpack
Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support loaders to preprocess files, i.e. json, jade, coffee, css, less, ... and your custom stuff.