As far as books, if you can pick some up, the two I recommend are Object-Oriented JavaScript, and JavaScript: The Good Parts. Both books lay out why JavaScript is different than any other language you might know. The former book focusses on how you can bend or work around it's peculiarities to so that you can think about your program in more familiar terms, while the latter focusses more on leveraging and embracing those same peculiarities as they are, because they're actually pretty nice for a lot of stuff. In fact, because of how it works, I consider JavaScript to be a really good language for scripting things (as in Unity) -- it may lack the popularity of e.g. Lua in gaming circles, but it works every bit as well, aside from the integration story (which Unity has already done for you).

But if you're looking for more of a "Learn to program using JavaScript" -- where the focus is on learning to program and JavaScript is basically the vehicle for that, I'm not aware of any books. Codecademy might be good, but I've never used it. W3Schools is really great, but focusses on using JavaScript in the browser. Khan Academy's programming resources seem to be mostly (entirely?) in JavaScript, and their material tends to be pretty good overall.

I reviewed the two books JavaScript books I would really recommend. The one is JavaScript:The Good Parts like Ravyne recommend and the other is JavaScript: The Definitive Guide. The second book is the all in one primer book, the kinda of book everyone needs to own. Unlike many books, only a 3rd ( of like 1200 pages! ) is about DOM programming, and nicely, its regimented well. This is the biggest flaw with a lot of JavaScript books, they seem to assume you want to work in the web browser only, which is annoying.

The Good Parts on the other hand is half a terrible book. The author is an arrogant douche, at least it comes across that way. Half of the book is trying to be overly clever by a half, the examples are convoluted for the sake of making the author feel clever, as opposed to easy to understand, like an example should be, plus the author states a hell of a lot of opinion as fact. So why then do I recommend it? The other half is pure gold. It's the JavaScript Equivalent of Effective C++. It *WILL* make you a better JavaScript programmer if you are capable of groking it. Plus its short and cheap.

That said, JavaScript:The Good Parts is completely useless to you until you actually learn the language. It will not make you a JavaScript programmer, but it will make you a better one.

JavaScript's popularity outside the browser is certainly on the rise. With Google shipping the V8 engine, you are seeing more and more JavaScript "applications". Of course Node is certainly popularizing server side JavaScript, while it is being used in gaming, from HTML5 games, to Unity and Moscrif