Vanilla List : The Vanilla Javascript Repository. A searchable repository of dependency-free JavaScript libraries. Over 100 projects and growing.
Ember.js : A JavaScript framework for creating ambitious web applications
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 ...
loglevel : Minimal lightweight logging for JavaScript, adding reliable log level methods to wrap any available console.log methods
Dropzone.js : DropzoneJS is an open source library that provides drag'n'drop file uploads with image previews.
Add Clippy or his friends to any website for instant nostalgia.