BI-Tools

If it is about Tableau and other BI tools (Cognos, Microstrategy, Pentaho, Domo, Qlikview, Power BI) it lives here.

Power BI

Video Tutorials

Analyzing and Visualizing Data with Power BI - The eDX course is free and good as a first overview, but doesn't go in-depth on DAX or M.

EnterpriseDNA - have a good/great YouTube channel for specific examples but also have a Complete Beginners training for Power BI and one for DAX which are good groundings and free.

Books

The Definitive Guide to DAX (Business intelligence with Microsoft Excel, SQL Server Analysis Services, and Power BI) by Marco Russo and Alberto Ferrari

PowerPivot and PowerBI The Excel Users Guide to DAX by Rob Collie and Avichal Singh

M Is for (Data) Monkey: A Guide to the M Language in Excel Power Query by Ken Puls and Miguel Escobar

PowerPivot Alchemy: Patterns and Techniques for Excel by Bill Jellen and Rob Collie

Blogs

powerpivotpro - a general go to source. You tend to find a lot of the other industry experts contribute or help out in the comments.

sqlbi - Marco Russo and Alberto Ferrari covering DAX/SSAS/MDX

Excelguru - blog by Ken Puls (M and Excel related topics)

Kasper on BI - All about BI, Modelling, DAX and MS BI by Kasper de Jonge