[KlaymenDK]

I'm probably too late to the game, but here goes anyway.

I feel that not enough people are mentioning outliners -- essentially lists within lists within lists.

My favourite one is Workflowy, which exists as both a web app and a mobile app. I have top-level nodes for the major areas of my life: personal, relationship, work, house, hobbies, etc; each is then further broken down into smaller topics until they end in actionable points. You can even share parts of your outline with others (with read-only or edit access); for instance, my kids's wish lists are shared publicly to avoid unwanted or redundant presents; I have also shared nodes with my coworkers as a canvas for group brainstorming.

Outlines also work well within a GTD (Getting Things Done) context.