A positioning engine to make overlays, tooltips and dropdowns better #hubspot-open-source
HTML5 <audio> or <video> player with Flash and Silverlight shims that mimics the HTML5 MediaElement API, enabling a consistent UI in all browsers.
pushState + ajax = pjax
For slim progress bars like on YouTube, Medium, etc
An HTML5 saveAs() FileSaver implementation
AngularJS 1.2+ native directives for Bootstrap 3.
A simple, in-browser, markdown-driven slideshow tool.
jQuery Mobile Framework
Light and responsive lightbox plugin with focus on performance.
Delightful, performance-focused pure css loading animations.
Micro check library
Keep multiple browsers & devices in sync when building websites. http://browsersync.io