Addy Osmani introduces backbone.js as one part of the toolkit for building mobile JavaScript web applications. Backbone is an MVC-like framework to structure your application, simplifies server-side persistence, decouples the DOM from data, succinctly separates apps into Models, views and routers and provides synchronisation between DOM, model and collections.
Andrew Dupont's Mix 2011 presentation shares his experience with working with messy JavaScript and how to work towards maintainable JavaScript. He covers separation of concerns, using custom events, MVC, templating and developing modular code.