Trello is a great service. I've always felt like notes and to-do list-type digital utilities were too cumbersome to use. You could jot something down on paper in a few seconds, compared to all the configuration usually involved in arranging to be digitally notified of something ("A reminder? What about? When? Are you sure?") iOS' initial iteration of its stock 'Reminders' app was a bad example of this, requiring a crazy amount of taps to configure the when and where of your desired nudge.
A while back I saw the developers of the great indie game Rust using this Trello service to organize the details of their project: to-do, doing, done; categories, priorities, etc. A couple days ago I signed up to see if it'd be any good for keeping track of my coding projects, and it's actually pretty fantastic.
Trello gives you these blank slates, called "boards" – any number of them you want, likely one per project you're tracking. On top of each board, you lay out lists, and cards within those lists, to categorize and prioritize your work. The UI is super modern, minimal and fluid, with instant response on most things; all the UI behavior TRULY makes sense. In a way it's odd that it took until 2014, but I think we're really getting there with UI on stuff like this. From a card, one click can add an auto-expanding list and position your cursor in the box for the first to-do item. Once you press enter that first item is bulleted and your cursor goes to a blank slot for item #2. You just click anywhere else when you're done. Unfinished edits to items are retained, but separately, so you can finish them before saving. Etc.
Give it a try, if you have some use for organizing sets of tasks or goals. I'm finding it useful for more than I expected I would.