What about using wiki to make documentation for the software which needs it? I made http://wiki.maemo.org/Geocaching page some time ago to help geocachers with gpxview and maemo mapper.

Then we as a community would just need to make page for each program in wiki and write the documentation. Developers then could add link in their software to that wiki page. I actually tried to start that with http://wiki.maemo.org/OMWeather but I haven't had enough time to do it yet.