A small Lisp written in C. Jeff kept a diary on his blog (https://blog.jfo.click/) while writing it.
A little interactive explorer for the CIE HLC colorspace, which has been suggested (by the freiefarbe.de people among others) as colorimetrically sound colorspace that's also well suited for communication.
A very simple version of the wave function collapse algorithm, which creates patterns that are locally similar to an input bitmap.
Exploring the Prolog programming language as a means to throwing the ideal dinner party.
An open source crossword puzzle app that lets you collaboratively solve puzzles in real-time with friends.
A simple, open source ad server for plugging your own projects.
The first post of an in-depth, a 10-part series on how to write a C compiler
What happens when computers try to imitate surrealism or humor?
rbspy is a profiler for Ruby. It lets you profile Ruby processes that are already running. You give it a process ID, and it starts profiling.
It's a sampling profiler, which means it's low overhead and safe to run in production.