FreeBSD Documentation Project: Documentation Set
FreeBSD’s documentation falls into three basic categories:
The manual pages are part of the base system, but are also an important component of the documentation. Both the Documentation project and source committers update and maintain manual pages.
At present, the Japanese team has translated many of the manual pages. Other volunteers could pitch in to translate the manual pages to other languages as well.
The project has a large amount of documentation that is "book length", or becoming that way. These include the FreeBSD FAQ and the FreeBSD Handbook.
FreeBSD has a wealth of information available in shorter, article form — similar to the tutorials or HOWTO documentation of other projects.