Visual Outliner

Visual Outliner is an outliner software for Windows, and it uses OPML as native file format.

NoteFly

NoteFly is a small advance note taking application that allows you to create sticky notes.

OmniOutliner

OmniOutliner is a writing app for collecting information, outlining ideas, adding structure to any sort of writing.

Tkoutline

Tkoutline is a single pane, cross-platform outline editor written in Tcl/Tk .

Trello

Infinitely flexible. Incredibly easy to use. Great mobile apps. It’s free. Trello keeps track of everything, from the big picture to the minute details.

Unclutter

Unclutter is an app that is designed to help Mac users bring order to their desktop. Among other features, this powerful piece of software provides quick access to a user’s notepad and clipboard.

wikidPad

wikidPad is an application for storing thoughts, ideas, todo lists, contacts, or anything else that user can think of to write down.