Ask HN: How do you document you stack?

I have a fairly large project and I want to make it as easy as possible for other developers who come on board to get a broad overview of the application's structure and behavior. Do you document your system in a single README.md file sitting in your app's root? Do you draw network topology maps? How do you go about documenting the intricacies and nuances of your program?

- Commenting code, obviously, helps a lot. - bash scripts that document the build environment are awesome. - A soft introduction in a README file.

Could I be doing thing smarter? Do you have any neat tools or processes you use?

Thanks.