Wiki’s (see wikipedia for a description) are a nice and easy way to document.
Because of the agility it’s easier to maintain documentation. I often encounter documentation in word, which has aged and is not accurate anymore. Sometimes changes occure which just do not get documented, sometimes it is documented, but in the version of the one who did the changes, which is not uploaded back to the document location. Or in another document location.
Traditionally, for a wiki you need a webserver, an application server and storage (either in a database or just on the filesystem). In some cases (think tomcat, jboss) the application server can act as a webserver also.
But what if you want a personal wiki (just to put your own (installation|modification)logs, scripts, links, and other data), and you want wiki flexibility, but not the difficulty of starting webservers etc.?
The maximal minimalistic approach is here: Wiki on a Stick, a wiki that consists of one self-modifying XHTML file.