Guest lecture Delft technical university
Since 2011, I've been giving yearly guest lectures at the Delft technical university. After starting my job at the Software Improvement Group I discovered that they have a program where they support student projects to help them improve software quality, called the Open Code Clinic. I found this interesting and immediately joined the program. Several years later this is still going, and in the intervening years I also started giving guest lectures for a more theoretical course related to software engineering methods.
Gaining this experience with teaching has been a great experience, that makes you think about aspects such as how to tell a story, how to understand the question behind the question being asked, how to try and convince people, and how to manage a large group of people. All of thse skills are of course also useful outside of education :)