As part of writing Zig, a new programming language to replace C, Andrew has also written a C compiler frontend with all sorts of tricks including seamless cross-compilation.
"Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae." Jesse made a Chrome extension to test this theory by jumbling the letters of words in your browser while leaving the first and last letter intact. Turns out it's not as true as you might have thought! You can install the extension here: https://chrome.google.com/webstore/detail/jumbletron/mkkhhidcfedbiofenhlnlhjpndfbcpmi
Sol implemented a raymarching rendering algorithm to draw fractals; they're beautiful! You can see the code on GitHub and more image examples here: https://gist.github.com/solsarratea/6c5166db6c70c5d09dbd4da52025f3e4
A better/faster search interface for the Messages app on macOS.
An extensive, clear explanation of how to write a lambda calculus interpreter in Haskell.
Book Wyrm is a federated alternative to Goodreads that lets you track what you're reading and share it with friends. Try it out here: http://fedireads-test.glitch.me/
A narrative scripting engine similar to Ink (http://github.com/inkle/ink), but more portable and implemented using Haxe.
Brian gives a deep explanation of how Monte Carlo Tree Search (a key technique for game AIs) works. He implemented the AlphaGo paper from scratch, so he should know!
A small, readable, self-hosted Lisp to C compiler.
A nice overview of Vim 8's native plugin support and how to migrate to it from Pathogen.