Digital Note-Taking
I originally conceived of a blog page for my website, but much as I like reading blogs, blogging does not come naturally to me. Also, if you have a subject you want to interrogate, what's the point in writing a single essay about it? That assumes you'll draw a definitive conclusion. I think a better approach is the living document: a record of your thoughts on a subject, updated as those thoughts come to you.
The other thing I like about this idea is that it aims your thinking at the future. When you write about a subject, the question is, "What can I learn from this, and how can I best explain it to myself so I can use it in the future?
This isn't my brilliant idea by the way. What I've just described is a digital garden. I just prefer to think of it as a notebook. I built mine with Foam.
Second-order Relationships
If A is related to B, and B is related to C, then A has a second-order relationship to C. But Foam doesn't generate these relationships.
As Kasey Klimes notes, second-order relationships are by definition less obvious than first order relationships. So second order relationships hold even more potential for surprising insights.