One of the most useful things I self host on my server is a personal wiki. I use it for note taking on projects, a journal, a beer homebrew log, storing recipes, config files, and for archiving web pages or documents. It is a great alternative to Evernote or OneNote if you want to keep your information out of the corporate cloud.
There are many wikis out there but I prefer the low-overhead DokuWiki, which is easy to install and uses flat plaintext files to store your wiki pages so it’s easy to set up anywhere and backup your data. DokuWiki as a default install is very basic and can be extended to do almost anything with a few plugins. Read below for some of my recommendations for making the most of your wiki and some example use cases.