Joe Zim's Javascript Blog has a great post on Marionette - the Backbone.js exoskeleton:
Backbone.js introduced us to a more modular way of developing today’s web applications by separating our code into semantic and reusable pieces. Backbone’s main crutch was that it offered only the bare minimum so that it was easy to learn and didn’t force you to do anything that you didn’t want to do, but we were left on our own to figure out how to handle much of the implementation details. Marionette is here to help with that.