Every Excel user who spends their days re-organising data must learn about Power Query (now called Get & Transform in Excel 2016).
It is so good that not knowing it will soon be career limiting.
Power Query (as I'll continue to call it for now) is the "gateway drug" to Power Pivot and PowerBI.com.
This article is for newcomers to PowerBI, to shed some light on what this suite of tools is capable of.
https://www.linkedin.com/pulse/what-power-bi-wyn-hopkins