If you are new to Excel or have never used it, use below links to come up to speed.

Intro to Excel
Tables
Structural Refs
Essential Formulas
Pivot Tables Intro
Have been using Excel for a while? Check out these tutorials to learn more and become awesome.
Advanced Excel
Pivots from Multiple-Tables
Multi-column Lookups
Interactive charts
VBA & Macros
Work with Excel a lot and know your game well? We have some very-advanced topics for you too.
Check out:

Array formulas
Excel challenges
Advanced Charting
Data Tables & Simulations
Power BI
Power BI is the most exciting thing to happen for your data since spreadsheets. If you are looking for a new skill to learn this year, I highly recommend Power BI. Check out below tutorials and get started today.

Introduction to Power BI – your first tutorial
Introduction to Power Query
Learn more – Power BI Page