[StuckDuck]

I think the gnome project deserves a mention here, their docs program is really complete, and covers many high level aspects of how to use the software. Most gnome apps also use it

[than3]

That may have been true at one point, but post Gnome 2 exodus, a surface look will look like its good, but any deeper look will show its outdated.

Its also not very maintainable/supportable, and while that is changing slowly, they've written themselves into a corner in some respects.