Introductory Level

• Codecademy

  Codecademy

  Codecademy is the easiest way to learn how to code JavaScript. It's interactive, fun, and you can do it with your friends.

• Getting Started with JavaScript

  MDN

  What is JavaScript and how can it help you?

• Programming – The Real Basics

  Dev.Opera Web

  Basic fundamentals of programming. Following articles introduce what you can do with JavaScript, best practices for using it, and more.

• JavaScript From the Ground Up

  Google Code University

  Video tutorial on making pages interactive with JavaScript

• JavaScript Best Practices

  Dev.Opera

  Learn about some of the obvious and (not so) obvious best practices when writing JavaScript.

Intermediate Level

• A Re-introduction to JavaScript

  MDN

  A recap of the JavaScript programming language aimed at intermediate-level developers.

• Eloquent JavaScript

  A comprehensive guide to intermediate and advanced JavaScript methodologies.

• Essential JavaScript Design Patterns

  Addy Osmani

  An introduction to essential JavaScript design patterns.

• The JavaScript Programming Language

  YUI Blog

  Douglas Crockford explores the language as it is today, and how it came to be.

• Introduction to Object-oriented JavaScript

  MDN

  Learn about the JavaScript object model.

Advanced Level

• Learning Advanced JavaScript

  John Resig

  John Resig's guide to advanced JavaScript.

• Introducing the JavaScript DOM

  Elated

  What is the Document Object Model, and why is it useful? This article gives you a gentle introduction to this powerful JavaScript feature.

• An Inconvenient API: The Theory of the DOM

  YUI Blog

  Douglas Crockford explains the Document Object Model.

• Advanced JavaScript

  YUI Blog

  Douglas Crockford looks closely at code patterns from which JavaScript programmers can choose in authoring their applications.

• JavaScript Garden

  Documentation of the most quirky parts of JavaScript.

• Which JavaScript Framework?

  StackOverflow

  Advice on choosing a JavaScript framework.

• Non-blocking JavaScript Downloads

  YUI Blog

  Tips on improving the download performance of pages containing JavaScript.

• JavaScript Guide

  MDN

  A comprehensive, regularly updated guide to JavaScript for all levels of learning from beginner to advanced.