Scala is a object-functional programming and scripting language for general software applications, statically typed, designed to concisely express solutions in an elegant, type-safe and lightweight manner. Scala is a possible successor to Java.

Programming in Scala, First Edition

A Scala Tutorial for Java programmers (PDF)

Scala By Example (PDF)

Programming Scala

Xtrace (Github)

Lift (Github)

Pro Scala: Monadic Design Patterns for the Web

Exploring Lift (published earlier as "The Definitive Guide to Lift")

the-lift-book PDF

WikiPedia:Scala_(programming_language)

Why Scala? talk (youtube)