Almond
A minimal AMD API implementation for use after optimized builds
Sea.js
A Module Loader for the Web
LABjs
Loading And Blocking JavaScript: On-demand parallel loader for JavaScript with execution order dependencies
Layzr.js
A small, fast, modern, and dependency-free library for lazy loading.
Script.js
Asyncronous JavaScript loader and dependency manager
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.