What's the best way to learn JavaScript (in web dev context)

As a web developer that primarily writes ruby, css, html and a bit of JQuery. I'd like to step up my game in writing Javascript. We're headed towards a client-side heavy world and I seem to be a bit behind with JS. It just feels archaic.

What are some books, guides, or tutorials that helped you become better at programming with JS and JS related libraries like JQuery, CoffeeScript etc... (in the web dev context).

Please share!