Vym is a mind mapping program. It is useful to organize thoughts and do structure work. In addition to that it has a lot of helpful shortcuts.
A mindmap is a multicolored and image centered radial diagram that represents semantic or other connections between portions of learned material. For example, it can graphically illustrate the structure of a thesis outline, a project plan, or the government institutions in a state. Mindmaps have many applications in personal, family, educational, and business situations. Possibilities include note-taking, brainstorming, summarizing, revising and general clarifying of thoughts.
VYM is available in Ubuntu official repository, search and install it from Ubuntu Software Center. After installation, find it under Applications -> Office -> VYM View Your Mind.