I like to think about software that helps you think. Knowledge management, wikis, outliners, task managers, mind-mapping tools, and so on. There's a piece of software called TheBrain (https://thebrain.com/) which I really like; it does a great job of letting you make connections between different topics that are connected in your mind.

However, I prefer the usability of an outliner. So I'm making a web app that is basically TheBrain but visualized as an outliner instead of a mind-map.

There's a prototype available here if the concept sounds interesting to anyone else: https://thinktool.io/