Sher Minn built an interpreter for the long-defuct "ART 1" programming language from the 1960s, and used it to recreate some of the earliest pieces of computer art. You can see the code here: https://github.com/piratefsh/art1.js
This is a program written in Python to generate and edit mosaic knitting patterns, with built-in validation based on whether the pattern is possible to physically knit! It's currently designed to build an 8 stitch by 8(16) row block, displayed as a tesselation in real time.
A brief history of the uses of popcount (aka 'the NSA instruction'), delivered at !!Con 2019.
A reimplementation of the SQLite database, written once in C, and again in Python.
A program for the HP7440A pen plotter which draws midi notes real-time as they are received ^^
An open source implementation of the board game Splendor.
A webring made to inspire Recursers to build an online home and share traffic among each other.
A tiny C compiler written in OCaml.
Interactively deform tesselated stars. You can see the code at https://github.com/jessechen/polypile