Dark Matter: A Primer (PDF) — An excellent academic paper detailing the numerous pieces of evidence we've accumulated on the actual, measurable existence of dark matter.

Too dry? Here's an excellent Reddit comment (citing the above paper) that breaks down the evidence into more plain English.

Maps — All kinds of global map projections with explanations. Most of the maps are interactive and some are pretty fun to explore.

APIs all the way down — An excellent talk on communication by Miki Rezentes from Gig City Elixir 2019

Writing a program that writes itself — Quines are fun!

Want to know the easiest way to save time? Use make! — make is often a forgotten tool in the command line toolbox. But it's powerful, useful, and making a comeback.