Sea.js
A Module Loader for the Web
RequireJS
A file and module loader for JavaScript
Nanobar
Very lightweight progress bars. No jQuery
Imagesloaded
JavaScript is all like "You images done yet or what?"
jQuery Pjax
pushState + ajax = pjax
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.