Beginner
Event Handling (eloquentjavascript.net)
What is JavaScript? (www.youtube.com)
What's a JavaScript Library? (www.khanacademy.org)
What is the DOM? (css-tricks.com)
Modern JavaScript for Ancient Developers (trackchanges.postlight.com)
Learn X in Y Minutes (learnxinyminutes.com)
Eloquent Javascript (eloquentjavascript.net)
Introduction to JavaScript (www.codecademy.com)
What is AJAX? (www.youtube.com)
Javascript Dog (htmldog.com)
Learn JS (www.learn-js.org)
Treehouse - JavaScript Foundations (teamtreehouse.com)
Front End Interview Handbook (github.com)
Robust JavaScript (molily.de)
How JavaScript Works (blog.sessionstack.com)
Codecademy (www.codecademy.com)
Idiomatic JavaScript (github.com)
JSON: What It Is, How It Works, & How to Use It (www.copterlabs.com)
Learn JavaScript (www.codecademy.com)
CoderMania (www.codermania.com)
Intermediate
Superhero.js (superherojs.com)
Human Javascript (read.humanjavascript.com)
Modular JavaScript (www.adequatelygood.com)
JavaScript: The Right Way (jstherightway.org)
Code Wars (www.codewars.com)
A Dive Into Plain Javascript (blog.adtile.me)
A re-introduction to JavaScript (developer.mozilla.org)
Fight Code Game (fightcodegame.com)
Advanced
Introduction to Object-Oriented JavaScript (developer.mozilla.org)
Learning Advanced JavaScript (ejohn.org)
Learning Javascript Design Patterns (addyosmani.com)