Free Software that I rely on. One per day.
Day 23:
Pelican (and Pelican Importer)
While I use Wordpress for my live Production Log, I also keep annual offline permanent archives on M-Disc media. For these, I need a static HTML site that I can read offline with a browser.
There are a number of static site generators, but I use Pelican. Partly because I'm partial to stuff written in Python, and partly because it has a really good import utility to get the content from Wordpress's XML export.
I also like that I can add articles in HTML, Markdown, or reStructuredText formats.
https://getpelican.com/
https://github.com/getpelican/pelican