Since a lot of people recommended docuwiki for setting up a quick and easy way to document stuff I wanted to give it a try!
As I own a recent QNAP home storage (which supports vhosts, php, … and all other required things) why not combine them

First, enable the webserver (Network Services -> Web Server) and then switch on vhost support.
Create a new vhost for your new docuwiki installation with port 80 and /Web/docuwiki as path.
Since the folder “docuwiki” is not created automatically, log into your QNAP with SSH and create the folder.

Find your way to the docuwiki website (https://www.dokuwiki.org/) and download the most recent version as tar.gz. You might want to use wget to download it directly onto you QNAP.

wget http://www.splitbrain.org/_media/projects/dokuwiki/dokuwiki-2012-10-13.tgz -O /share/Web/docuwiki/dokuwiki-2012-10-13.tgz

Extract the tgz file into /Web/docuwiki and point your browser to http:///docuwiki
The build-in installer should come up and ask you some simple things.
If docuwiki is not happy with some of your folder permissions, add write permission to the listed folders with chmod

Have fun!