Kaggle Learn is easily the most impactful thing I did during the nine months I worked at Kaggle.
I contributed two microcourses, one on data analytics and one on data visualization (now archived), both in Python, to this online learning initiative. These courses eventually reached 200,000 plus learners.
I still get emails from time to time from acquaintences or friends-of-friends that took my course on Kaggle. It's been a pretty humbling experience!