Although Christian Heilmann covers what he wished he knew about JavaScript earlier, he actually points out the features JavaScript developers should know: shortcut notations, JSON, native JavaScript functions, event delegation, anonymous functions and the module pattern, allowing configuration, and using good libraries to abstract away browser differences.
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.
Another Douglas Crockford video. This time Douglas talks about the Document Object Model, about how Java failed, and JavaScript evolved thanks to DHTML and DOM. He talks about how to use DOM to traversing and manipulating elements in an HTML document, walking the DOM, making elements, innerHTML, as well as Events, memory leaks. He talks about the cracks in DOM, and how we must be prepared to back off when we hit the browser limits of DOM.