I found "Learn X in Y minutes" (www.learnxinyminutes.com) while researching the programming languages needed for a new project. The site aims to help people who know at least one programming language to learn others by proving a quick run through of the main language features. It's not quite enough to get you up and running. After all, having sample code doesn't get you the compiler. However, it's a nice start that shows you how similar (and different) language X is compared to the one(s) you already know.
If you're interested, I've been looking at Java and Scala. I will explain more about why in a few weeks' time.