Most people agree that rsyslog is a decent and useful piece of software. However, most people (including me) also agree that the rsyslog documentation is, ahem, sub-optimal.
When I code, I always think "I'll do the doc soon". But when "soon" arrives, something else is in the way. Yet another (justified) feature request, articles and other projects (yes, they exist ;)). At least I try to convey the important concepts and backgrounds here in the blog, but you have a hard time if you intend to extract a specific feature from the blog. So: the doc is in a bad shape.
I just got an offer from an volunteer who would like to help with the doc. That may even be the start of a rsyslog doc team. In any case, that's a fantastic opportunity. First of all, more doc means more and happier users. Secondly, I think it is very useful when someone other than me writes user doc. I can't even envision the questions that a regular user may ask, and this is a problem for any manual I write.
I hope this collaboration manifests. In order to aid it, let me briefly describe what currently exists: www.rsyslog.com is driven by Postnuke for various reasons, the most important one that I have a postnuke wiz at hand, so I do not need to dig in any dirty details if I need something extra ;) Postnuke is a CMS, so dynamic content can be added and is easy to edit by anyone else. So far, we use the web site itself primarily for news announcements.
The real doc set is kept as HTML. We use a Postnuke module to integrate that static html into the CMS. The HTML doc set exists only once, right inside the rsyslog git tree. When I make changes, they automatically go into git, go into the tarball and I also copy them over to the web site. All of this is without any effort, which is good. The bottom line is that the HTML doc set needs to be modified by patches or me pulling from someone else's git archive (both of which I will happily do). I think it is good to have the html pages available in the tarball, previous discussion on the rsyslog mailing list showed that package maintainers think so, too.
There exists two man pages. They are extremely bad. They need to be hand-synced with the html pages and I almost always forget to do so. Man pages do not go onto the web (besides some very old copies I produced via a clumsy way). But the live in git and the tarball, too.
A partial effort was done to internationalize the doc set, based on the usage of docbook. I think this is a good approach and the work done so far is kept in the rsyslog docbook branch. However, the approach currently focuses on the man pages. I do not know if it will work for the HTML doc, too.
I find docbook a very interesting concept, but the learning curve is steep. I simply had not enough time yet to dig deeply into it to start any serious work with it (html and LaTeX are still king for me ;)).
We have also a few places of obviously user-contributed content, the most important one being the rsyslog wiki. It contains many useful things, among others config samples. The bad thing about the wiki is that there is only a single one. So it probably is not the place to describe things that are very version dependent. Or is it and I have just the wrong approach - correct me!
Worth mentioning is also the rsyslog knowledge base, which primarily focuses dynamic content and discussions. But the search function is a very useful tool. Also, part of the larger knowledge base is devoted to gather information on how to configure syslog devices, how to best react to messages and how to consolidate e.g. Windows events. This obviously is not direct rsyslog documentation, but I hope it is useful and will continue to grow even more useful.
Finally, there is the mailing list and most importantly the mailing list archive. While this is definitely not considered a documentation resource, the archive has a lot of valuable information and it may even be a starting point for creating "real" doc.
I hope this is a good and complete wrap-up of the doc situation. If I have forgotten anything or you'd like to tell me your thoughts: just use the comment function! :)