Most open source Free Software projects have their own Help Forums and Documentation Wikis.
Help Forums are often very active: users from around the world flock to them asking for help: either the documentation is insufficient, there is a bug in the software, or the user doesn't know how to use it. Often, too, a few dedicated people do their best to answer the questions of many users who come when run into a problem, and leave when their problem is solved.
Documentation are now often kept within Wikis. It takes time to write a proper documentation, so the community of users is often invited to contribute what they can to it.
Unfortunately, the tendency is that Forums (or mailing lists) are often overused, and wikis underused. When facing a problem, people come for support in the forum, get their answer and go away. The documentation wiki, though, doesn't get any better. It'd be a good idea to encourage people to take a commitment to update the wiki with the answer they got (especially if others are likely to have a similar question, bugs being excluded).
See links below for proposals and discussion on this topic.