Trello has both free and paid plans; for solo work, the free plan works fine and I especially like being able to drag & rearrange "cards" from board to board and list to list. There are plenty of bells & whistles I don't bother to use, but for basic tasks, it's pretty intuitive.
I'd love to be able to delete a card instead of simply archiving it; sometimes I just change my mind and would prefer to wipe the slate clean.
Also, in its standard configuration, Trello lists appear in one huge horizontal layout across your screen (and far beyond). So I combine it with a Chrome plugin called "List Layouts for Trello" which allows lists to be laid out in a grid structure. This works far better for me.
Someone who prefers a slightly more visual to-do list and enjoys dragging & dropping when planning their work.