Yeoman is one of the cool kids in the yard, a combined effort of a lot of respectable developers to provide a tool that simplifies the setup and management of web app projects: less time spent in learning X different tools, more consistency and ease of use.
There are a lot of points of interest in Yeoman, the most important of them are:
Building an Yeoman project is easy. First, install it:
$ curl -L get.yeoman.io | sh
Then enter in an empty directory and type
$ yeoman init
This will present you a welcome screen, and a list of options of what you'd like to add to the project.
You can start a new Ember.js project by typing
$ yeoman init ember
This creates a new Ember.js app, creates a basic set of models, controllers and views/templates (and their directories), adds the script tags for all dependencies (jQuery, Handlebars) and creates an index.html file based on the HTML5 boilerplate project http://html5boilerplate.com/.
You can use Yeoman to bootstrap the project, update dependencies in your project, run tests and so on. And, when the project is ready for deployment, you can take advantage of Grunt https://github.com/cowboy/grunt built in Yeoman by calling "yeoman build", so that it lints, compiles everything for production, concatenates and minifies script and styles, compresses images and so on.