Brent Ozar – The SQL Server Posts You Read the Most in 2021
Brent Ozar’s posts on SQL Server are top-notch, and many of his recommendations to apply to other SQL engines

SQL BI – Displaying Filter Context
SQL BI is my go-to for most things related to Power BI models. Understanding what is filtered is good for troubleshooting as well as informing the end-users what is being filtered

dbt – Getting Started Tutorial
dbt is a way to programmatically perform ETL and is a useful tool for any data engineer or data scientist. Bonus points for it being open source.