There are plenty of CMS choices today (a great many of which are free). For many types of projects, a Wiki acts as a great CMS, because anyone can edit. Wikis are nice, too, because many of them keep a revision history. Lots of open source projects use Wikis with the idea that users of the project can contribute documentation.
The trouble with a wiki, though, is that even though a revision history is maintained there’s no way to sync up the wiki with the versions of the software people are using. Or, at least, there’s no way built in to the wiki to do so.
I was thinking that a CMS or wiki that stores its content in subversion may offer the benefit of subversion’s branching and tagging. Lo and behold, I find that there’s a CMS called Sitellite that can store content in subversion (or CVS, but why use CVS these days?)
It would be interesting to see if Sitellite actually lets you tag your content and present older versions in an organized manner…