macosxhints - 10.4: Use the Finder as an outliner
: "So, what is the perfect outliner? I wanted it to be project related. Ideas and project files should be organized in one simple way. I tested many outliners, but they all had the same problem: some stuff stays in the Finder (important but unsupported project files like Freehand, Illustrator etc.) and other stuff (ideas, mindmaps, notes...) goes into the outliner.
So you need the Finder for the project files, and the outliner as a conceptional layer. That just didn't feel right. I think the Finder is still the best way to organize files and folders for projects. So I just needed some way to store text and multimedia in one file inside these project folders ... and there is a somewhat obvious way: .rtfd files.