OmniOutliner is one of my favorite and most frequently used Mac apps. It is indispensable for preparing writing outlines, lectures, talks and project plans. There is plenty of other outlining software (often combined with mind-mapping), but none matches OmniOutliner in its simplicity, elegance and power.
At first sight, OmniOutliner is very simple: you can create headings of different levels, move them around and “collapse” or hide lower level headings to get a higher-level overview of your outline. By pressing ⌘-’ or a little icon next to an entry you can insert a text note related to that entry. There is also a possibility of “hoisting” or displaying only one heading and its children if you want to work with just one part of your outline. This is pretty sufficient for a large part of simpler outlines. But there is much more to OmniOutliner.
First, bringing up the Inspector gives you a lot of possibilities for formatting and customizing your outline: from the numbering style of sections to background colors, headings and much more. Secondly, a formatting panel on the left not only contains a “table of content” for your outline, but also allows you to define custom styles depending either on the level of entry (e.g. make all 1-st level headings bold and blue) or associated with a function button. For example, in preparing talks I want to highlight entries associated with pictures in my slides, so I set up F1 to make an entry background yellow and press F1 every time I add a note concerning a new picture in my presentation. OmniOutliner also allows to save outlines as templates and then start new outlines based on an already existing template to avoid starting all this customization anew. I have templates called Writing, Presentation, and Planning.
Thirdly, by default OmniOutlines has only one column, but you can easily add other “dimensions” to your outline by introducing additional columns. For example, you may want to keep an outline of your article and track who is responsible for each section. You could introduce a second column called “Responsible” and format it as a drop-down list of names of all co-authors. Another example, for project plans you may want to keep start and due dates of individual tasks.
Finally, OmniOutliner smoothly integrates with other software. It’s pretty easy to add a weblink, an email, or attach a file to an outline entry. Outlines can be exported to many formats, particularly useful is the Keynote format (where the top-level headings become individual slides) and the OPML format which is “understood” by Scrivener and many mind-mapping applications. As easy to guess from the names of my templates, I use OmniOutliner for outlining writing, preparing lectures and talks, and project management.