We have documentation for Cactus and the ET on their respective websites. This should be updated automatically when the source is changed, so it is never out of date. There should be documentation for the current release as well as the current development version.
There is one technical problem standing in the way of this. The system should be automated, and it needs to have commit rights to a specific directory in the SVN repository hosting the files. SVN accounts for CCT machines tend to be the same as CCT login accounts, so we don't want to store the username and password. I think the best solution is to create an SVN account specifically for the documentation build system which is not tied to a CCT login account. This account would be given commit access to just the directories necessary.
The "checkout, build doc, commit" script should be kept in version control somewhere, and a machine should be chosen on which to run it. It could be run regularly, or just in response to commits.