RequireJS : RequireJS is a JavaScript file and module loader. It is optimized for in-browser use, but it can be used in other JavaScript environments, like Rhino ...
yepnope.js : A Conditional Loader For Your Polyfills!
InstantClick : InstantClick is a JavaScript library that dramatically speeds up your website, making navigation effectively instant in most cases.
SPF : A lightweight JS framework for fast navigation and page updates from YouTube
Zepto.js : Zepto is a minimalist JavaScript library for modern browsers with a largely jQuery-compatible API. If you use jQuery, you already know how to use Zept...
Load scripts like images. Use HTML5 and CSS3 safely. Target CSS for different screens, paths, states and browsers. Make it the only script in your HEAD. A concise solution to universal issues.