I can't believe I never mentioned Sproutliner before. It's a free, online outlining web app that's surprisingly robust. It gets even better because its creator open-sourced it recently. I liked the hosted option, but it's very openness made me unable to use it for sensitive matters. Now I can host it on my own site, put it behind some authentication, and use it to my heart's content.
It took a little doing because I didn't install it into the root of my domain. The developer made it so that every link and reference was root relative, i.e., "/some-path/some-file.php". There were a lot of those references, so it took awhile to hunt them down—a global replace didn't work, unfortunately—and make them plain ol' relative.
