You can use brainstorming or mindmapping software to do everything from narrowing down a larger topic, to preparing a search strategy, to organizing your thoughts and notes for an outline. This last use fits in well with most sloppy note taking methods. Mind mapping is also a two dimmensional alternative to traditional, hierarchical outlines.
Bubble.us produces shiny, colorful bubbles and requires no sign in. It is extremely easy to use, though it has few options beyond color and size. You only get one sort of shape. The illustration at the right shows a mindmap used to narrow down a common paper topic by asking it questions. Click the illustration to see it at full size.
Draw.io/Diagrams.net and Mindomo both offer many more options for shapes lines and extra place to put text. Mindomo will not let you move your first shape, and Draw.io/Diagrams.net asks that you store your files in Dropbox, Microsoft Onedrive, or Google Drive. An image of a Draw.io diagram for a paper on dream interpretation is on the right and the image below is a partial outline for a paper on vaccine hesitancy made with Mindomo.