Dustin Ryan works at Microsoft and he shares a lot of his knowledge for free on his website.
This great site has lots of free content to help you get the most out of Power BI – from beginners to old hands.
Free videos and other content make this a great site to bookmark and check regularly.
It covers a lot of other topics that are related to Power BI as well.
Enjoy!
Please note: I reserve the right to delete comments that are offensive or off-topic.