Doug Crockford, Chief JavaScript Architect at Yahoo, did an excellent four part video series (each about 30 minutes long). Doug has a nice presentation style and covers most of the foundational elements of the language. There is a lot to learn here for ActionScript 3.0 programmers because of the common ECMA Script foundation in both languages.
Part 1 of 4
Part 2 of 4
Part 3 of 4
Part 4 of 4
The JavaScript lectures by Chandima Cumaranatunge, unless otherwise expressly stated, is licensed under a Creative Commons Attribution 3.0 United States License.
I was amazed at the detail of knowledge that could be presented in these four 30 minute videos. As it moves to ECMAScript standards, most of the design patterns we talk about are applicable to JavaScript.