Gulp.js - Automate and enhance your workflow
Grunt - The Grunt ecosystem is huge and it's growing every day.
Assemble - The static site generator for Node.js, Grunt.js and Yeoman
Webpack - Webpack is a module bundler. Its main purpose is to bundle JavaScript files for usage in a browser, yet it is also capable of transforming, bundling, or packaging just about any resource or asset.
Yogini - A cross-platform layout engine, by Facebook
Gear.js - Easy to use, simple to extend, and powerful build system.