RequireJS
A file and module loader for JavaScript
Lazysizes
High performance and SEO friendly lazy loader for images (responsive and normal), iframes and more, that detects any visibility changes triggered through user interaction, CSS or JavaScript without configuration.
Lazy Load Xt
Lazy load XT is a jQuery plugin for images, videos and other media
Px Loader
PxLoader is a simple JavasScript library for creating preloaders and resource downloaders for HTML5 apps.
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+.
Query Loader2
Version of the QueryLoader by Gaya Design. Preload images with ease.