Reqwest is a wrapper for asynchronous http requests. Includes support for xmlHttpRequest, JSONP, CORS, and CommonJS Promises A.
FinderJS is a small UI component that allows you to browse tree-like data in columns, similar to the file manager in OS X. It supports both static and asynchronous data sources and is easy to customize.
JAIL is a jQuery plugin that lazy load images making your page load faster. Images are downloaded when they are visible or when they become visible inside the viewport
LoadJS is a tiny async loading library for modern browsers. It has a simple yet powerful dependency management system that lets you fetch files in parallel and execute code after the dependencies have been met.
Verify.js is a powerful, customizable asynchronous form validation library.