This is probably irrational, but it's always annoyed me that Yeoman is little more than a package.json file and small bash script yet has a professionally designed logo.
There's yo (that scaffolds via generators), 10 officially supported generators that work with common webapps setups (e.g. angular backbone ember chrome-extension mocha karma), and (so far) 74 generators in the community building off this platform: https://npmjs.org/browse/depended/yeoman-generator
Then other supplementary modules: grunt-contrib-compass, grunt-contrib-imagemin, grunt-contrib-htmlmin, grunt-contrib-livereload, grunt-regarde, grunt-svgmin, grunt-contrib-connect, grunt-bower-requirejs, grunt-usemin, node adapters for optipng and jpegtran, configstore. This grunt infrastructure designed and maintained by the project.
In addition, the Yeoman also collaborates very heavily with the Bower and Grunt projects, both of which are accellerating very fast. There is considerable overlap in the core dev teams here, everyone working together amongst this disparate but congealing webapp developing tooling ecosystem.
This is Yeoman: https://github.com/yeoman/