There's no shortage of Node.js tutorials out there, but most of them cover specific use cases or topics that only apply when you've already got Node up and running. I see comments every once and awhile that sound something like, "I've downloaded Node, now what?" This tutorial answers that question and explains how to get started from the very beginning.
What is Node.js?
A lot of the confusion for newcomers to Node is misunderstanding exactly what it is. The description on nodejs.org definitely doesn't help.
A great guide for a guy like me who knows how to spell Node.js (mostly) but that's about it...