I write technical non-fiction and find that I cannot write well without first constructing a detailed (10-20 page) outline. Are there any good outlining solutions for OSX? Apps? Templates in Microsoft Word? Etc.
Am I allowed to beat the drum for Scrivener again? :)
Scrivener is a tremendously flexible writing program which allows you to rearrange your items easily, by dragging around icons, by putting up virtual cards on a corkboard, or setting things up in outline format (the Outline view is right in the top bar). Each item of your outline is a document, which can then be filled in as needed, and moved around if you want.
You can download a completely functional version and test-drive it for 30 days, I think, to see whether you like it.
I have been doing a lot of my outlining/pre-writing work in Workflowy. It is technically a TODO app, but I like the bulleted and nested lists for outlining and refining. I sometimes write entire papers within Workflowy, using the nested zoom to refine and re-structure sections and paragraphs. You can export (via copy-paste) to other writing apps (msword, google docs, etc.). Be careful though, it is online only and "in the cloud." I've had it go down when I needed stuff I've written so I highly recommend regularly backing up your entire workflowy to a text document.
OmniOutliner. It is an absolutely amazing and flexible outlining tool for OS X. It also works well with OmniGraffle, say if you want to generate a graphical representation for the outline. More here: http://www.omnigroup.com/products/omnioutliner/. The professional version is better than the standard, as I recall, in particular because it allows folding the parts you are not working on.
I spend a lot of time in Tinderbox ( http://www.eastgate.com/Tinderbox/ ) It is a great tool for harvesting information, putting down ideas or any kind of notes. Then, as need arises, to structure this information, discover new relationships and patterns, and finally export it to text or html. It is great for taking notes at lectures and rework them later and for making sense of any problem whith lots of information.
You can jut notes down in map view, where notes look like sticky notes on a windowpane. There is an outline view where notes are viewed as lists. There are also several other views. You can make Tinderbox do many things for you – agents are notes that collect aliases of notes based on your chosen criteria. All in all, you can do a lot in Tinderbox. I find it is ideal for when you want to take notes, research, and when you want to think what you have researched into something good.
I can highly recommend Circus Ponies Notebook. It uses the notebook metaphor and it has a page type that gives you an outliner. You can easily integrate media files as well. I use it for fictional and non-fictional writing, then put my outliner next to Scrivener to write it down (CPN has the advantage of optional checkboxes for each cell, so you always know what you have already used). You can also use keywords to make sure you remember your sources, and of course, non-relevant parts can be folded in. While I love Scrivener, I need an outline that is more detailed, one information per cell. The files in Scrivener contain more than one idea when I write which makes it difficult to shift information.
This posting on my blog http://www.organizingcreativity.com/2009/09/circus-ponies-notebook-the-best-tool-for-structuring-creative-writing-projects-esp-research-projects/ gives a nice overview of its functions, there's also an example linked at the end of the posting.
While Scrivener is very useful for structural outlines, Circus Ponies Notebook excels at Content Outlines. There a posting in my blog comparing the outlining feature in both programs: Outliner in Scrivener vs Outliner in Circus Ponies Notebook — Structure (Scrivener) vs Content (CPN) Outlines
Frankly I couldn't have written my diploma, nor my PhD thesis, without it.
Not enough points to add to Lauren Ipsum's answer, but I really do like Scrivener. It takes some time to get your head around, really. As you're calibrating to it, it can at first seem too simplistic, or overly complex, but it's really a whole bag of amazing.
Not only will Scrivener allow you to outline and rearrange, but it also lets you store reference material, and add notes to your text, so it's way more than simply outlining.
I tend to write outlines using emacs and org-mode, because I do technical research that involves a lot of programming, and as a result, I live in emacs. Aquamacs is an emacs port for OS X that's free and has a nice Mac interface you can use instead of many of the Unix-based keyboard shortcuts. Aquamacs comes with org-mode, which is a nice text-based format for outlining and text-folding (so you can hide various parts of your outline). What I like about text-based formats is that it's easy to determine exactly what changes have been made between revisions (hell, if you want to track versions, use a version control system like Mercurial, Git, Subversion, etc.).
The advantages are that it's free, and highly customizable (up to a point). The outlines are exportable to a number of different formats.
The disadvantages are that the workflow tends to be designed for people who are programmers, and work in emacs. There's not much of a GUI to speak of, beyond the toolbar at the top of the screen (and each window). Emacs is written to be a highly flexible text editor, and org-mode is a plug-in; it's not designed to be something like Scrivener, which, as far as I can tell, bundles together all of the tools that they think writers need (and in a cool-looking way). If you want something to keep track of your sources or research, you'd need another program (like Mendeley, for instance, which does a pretty good job of acting as a database for PDFs and media). If you want version control, you need another tool for that. I don't know of anything that corresponds to the "corkboard" functionality. So if you want extra functionality, you need other programs to fill in the gaps.
I'm the author of Scribe, an outliner for Mac OSX. I'm happy to offer some free copies if you write me (see website).
I built Scribe because most outliners don't feel like native text editors. There's a separate text field for each item in the outline. Always found that distracting.
Scribe hooks into the native text system on the Mac and builds an outliner over it. My hope is that this makes the outlining experience much more intuitive.
Scribe has a native file type that supports audio recording synced to your outlines, but also exports as rich text and OPML. Scribe also can edit OPML documents.
It also supports iCloud.