One thing that Scala.js has lacked heretofore is a really solid *book*. There's a decent tutorial and a bunch of other useful information on the main website, and a growing body of community knowledge, but getting started looks a bit daunting, which is unfortunate: it's not actually a terribly hard technology to get started on, especially if you already know some Scala.
As these sorts of books go it's pretty short (not having a publisher pushing up the page count helps), but it's still a book rather than an article: expect to take a while going through it. And please note that this a draft, albeit a late one: it's akin to a late-stage MEAP, so don't be surprised by an occasional typo.
Recommended reading to anyone who wants to keep their skills sharp and is interested in Web programming. IMO, Scala.js is one of the most important parts of the Scala ecosystem, and very much a tool whose time has come. Having a good guide for getting started in it should only make that better...