Learn DAX Basics in 30 minutes!

Now is the time to start with DAX: a few days ago a tutorial has been released to help you learn DAX basics quickly.
The QuickStart: Learn DAX Basics in 30 Minutes is available as part of the MS Technet Wiki, so we can all contribute to it also!

This QuickStart is for users new to PowerPivot or tabular model projects authored in SQL Server Data Tools. It is meant to give you a quick and easy introduction on how you can use Data Analysis Expressions (DAX) to solve a number of basic data modeling and analytical problems.