The Scala Programming Language has been around some time and started getting popular in 2007. A good place to start are the tutorials included in the distribution, which are also available online: A Scala Tutorial (very short 15 pages), Scala By Example (already 145 pages) and The Scala Language Specification (full 180 pages).
Early multimedia resources that picked my interest were Martin Odersky's talk, The Scala Experience at JavaOne 2007 and the 62th episode from Software Engineering Radio. Further Martin Odersky gave another talk at JavaOne 2008 and JAX'08.
In January 2008 Ted Neward began his busy Java developer's guide to Scala, which started with stuff from the Scala Tutorial but went into greater detail later. Another blogger that is definitely worth mentioning is Daniel Spiewak, who wrote the nice Scala for Java Refugees as well as on some special topics like Integrating Scala into JRuby. Another piece worth recommending is Dean Wampler's blog titled the The Seductions of Scala. James Iry has to be mentioned for exploring more theoretical stuff in nice little chunks.
After spending some time with Scala, I went for the only book available, Programming in Scala, a comprehensive step-by-step guide with massive 754 pages. Unfortunately it did not ship for almost 9 (!) months and I do not like ebooks. (I know - I should have read the whole page when ordering; that it was not printed, not even finished back then.) However, now it's printed. Since January it's standing on my book shelf and torturing my conscience.
I have to pull myself together and finally start reading it!