1. Taking a typing class my freshman year of high-school, and learning to touch-type way back then (1987-1988)
2. Learning Java. I started dabbling with Java on my own time, well before it became part of my work life, and from a career perspective I really can't complain. This is not to say that Java is the be-all / end-all, or even my favorite language - but in terms of putting $$$ in my bank account, it worked out really well for the past 20 years or so.
I'll also add another seemingly weird one:
3. Joining a volunteer fire department and being a firefighter for about 10 years. I don't really have time to do justice to this one here... maybe one day I'll write a blog post about it. But while being a volunteer firefighter contributes nothing to one in direct financial terms, I'll just say that I found it to be an incredibly enriching experience. And the lessons I learned while firefighting have had an impact on the rest of career and life.