Bruce Paul's starred repositories
freeCodeCamp
freeCodeCamp.org's open-source codebase and curriculum. Learn to code for free.
You-Dont-Know-JS
A book series on JavaScript. @YDKJS on twitter.
webpack
A bundler for javascript and friends. Packs many modules into a few bundled assets. Code Splitting allows for loading parts of the application on demand. Through "loaders", modules can be CommonJs, AMD, ES6 modules, CSS, Images, JSON, Coffeescript, LESS, ... and your custom stuff.
You-Dont-Need-JavaScript
CSS is powerful, you can do a lot of things without JS.