Chris Webster already assembled some good resources. Here are my 2 cents.
Cay Horstmann's book is over 300+ pages, so it's not really a quick start. Besides, it's only about the syntax and doesn't cover everything, so I would skip it in favor of "Programming in Scala", which is a must read anyway.
Coursera's "Functional Programming Principles" is not really about Scala. For some reason, people don't pay much attention to its title, but it actually reflects its purpose pretty accurately. It's basically "Structure and Interpretation of Computer Programs" repackaged with Scala instead of Lisp/Scheme. Since it's based on a course for absolute beginners, experienced developers will probably not learn anything practical (it says "Principles of ..."). It's a decent course to learn basic FP stuff, but in terms of Scala you will probably learn more in one hour of watching this video:
Obviously, this video is a hack as the author probably doesn't use Scala for work, but it's an efficient way to pick up the basics. Alternatively, you can start with the free sample from my book:
The sample is about 45 pages and it contains everything you need to know in terms of syntax and FP basics.
With these resources, Scala basics can be picked up in hours as opposed to weeks/months.