Aren't there any tools which could analyze a code base and generate a project map / graphical class overview with dependencies a.s.o.?
Yes, there are, but these are in general useless, since they don't really describe how the software works. Process diagrams and tutorials are far more useful.
Well I think, the big picture documentation can only be done by people who at least have enough overview on the project and its history.
True, but we still need someone who is willing to take overall responsibility of the documentation and find the bits that need to be documented. Also clean it up once someone writes some documentation, and makes sure it is organized well and is up to date. I'm happy to contribute when someone says that "this bit here, that needs contribution from YOU since you understand it", but I can't take on the entire project management of the documentation, too...
/Janne
