OmniOutliner!

Workflowy lets you organise your brain into easily manageable lists. It also works as a single-pane outliner with inline notes. It offers one-click hoisting (zooming into branches). The online version syncs with mobile apps.

A hierarchical note taking application, featuring rich text and syntax highlighting, storing data in a single xml or sqlite file.

wikidPad is a Wiki-like notebook for storing your thoughts, ideas, todo lists, contacts, or anything else you can think of to write down. What makes wikidPad different from other notepad applications is the ease with which you can cross-link your information. Links in a wiki are created by typing in WikiWords. A WikiWord is any mixed case word typed into the editor. TodoList or JohnDoe are example WikiWords. The term wiki means "quick" in Hawaiian, and wikis are all about quickly linking your information together. Wikis are not a new concept, in fact there are many web based wiki servers avai »

Dynalist is the easiest way to be organized and stay on top of things.

Org-mode is for keeping notes, maintaining ToDo lists, doing project planning, and authoring with a fast and effective plain-text system.

NixNote, formerly Nevernote, is an open source client for Evernote . It is written in Java so it will also run on Windows & OS-X, but the primary focus has been to try and get a usable environment for Linux.

EssentialPIM lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.

Checkvist is a web tool for creating online outlines, hierarchical task lists, collecting and structuring all kinds of information. It has an outstanding keyboard support so you can easily re-structure your lists, filter, hoist and beef them up with tags, due dates, links, or attachments. Collaboration, Markdown, code highlighting, import and export (OPML, text) make Checkvist an ideal hub for working on complex IT projects.

Piggydb is a Web notebook application that provides you with a platform to build your knowledge personally or collaboratively. With Piggydb, you can create highly structured content by connecting knowledge fragments to each other to build a network structure, which is more flexible and expressive than a tree structure. Fragments can also be classified using hierarchical tags.

MyLifeOrganized (MLO) is a personal task outliner and to-do list manager which will help you to organize your goals, projects and tasks into a tree.

Manuskript is an open-source tool for writers, with outliner, character management, plot development, distraction-free editor, etc. OutlinerOrganize your thoughts and snippets in a hierarchical manner. Organize them as you wish, reorganize them on the go.

Moo.do is designed to be the best and easiest way to keep your life and thoughts organized: projects, to-do lists, appointments, contacts, reminders, events, and anything else you want to write down. As all modern apps should be, Moo.do is available on any computer, tablet, or phone and synchronizes all devices and users in realtime.

KeepNote: note-taking and organization. KeepNote is a note taking application that works on Windows, Linux, and MacOS X. With KeepNote, you can store your class notes, TODOlists, research notes, journal entries, paper outlines, etc in asimple notebook hierarchy with rich-text formatting, images, and more.Using full-text search, you can retrieve any note for laterreference.

UV Outliner is a small and powerful single-pane outliner. It is intended for creating, organizing, and collecting information.

germ.io is a project management tool that is centered around ideas and taking them through to execution.