Nanobar
Very lightweight progress bars. No jQuery
jQuery Pjax
pushState + ajax = pjax
Layzr.js
A small, fast, modern, and dependency-free library for lazy loading.
Head js
The only script in your HEAD. Head JS loads JavaScript files in parallel like images without blocking the page. Your page will be faster. Even with a single combined file.
Script.js
Asyncronous JavaScript loader and dependency manager
LABjs
Loading And Blocking JavaScript: On-demand parallel loader for JavaScript with execution order dependencies