I've been promising myself that I'd do a series of articles about tools that I've incorporated into my exocortex over the years, and now's as good a time as any to start. Rather than jump right into the crunchy stuff I thought I'd start with something that's fairly simple to use, straightforward, and endlessly useful for many purposes - a wiki.
Usually, when somebody brings up the topic of wikis one either immediately thinks of Wikipedia or one of the godsawful corporate wikis that one might be forced to use on a daily basis. And you're not that off the mark, because ultimately they're websites that let one or more people create, modify, and delete articles about just about anything one might be inclined to by using only a web browser. Usually you need to set up or be given an account to log into them because wiki spam is to this day a horrendous problem to fight (I've had to do it as parts of previous jobs, and I wouldn't wish it on my worst enemy). If you've been around a while, when you think of having a wiki you might think of setting up something like WikiWikiWeb or Mediawiki, which also means setting up a server, a database, web server software, the wiki software, configuring everything... and unless you have a big, important project that necessitates it, it's kind of overkill and you go right back to a text file on your desktop. And I don't blame you.
There are other options out there that require much less in the way of overhead that are also nicer than the ubiquitous notes.txt file. For the past couple of years (since 2012.ev at least) I've been using a personal wiki called Tiddlywiki for most of my projects which requires just a fairly modern web browser (if you're using Internet Explorer you need to be running IE 10 or later) and some room on your desktop for another file.