I'm currently learning Rust in my spare time by writing a terminal-based text editor, ped. This led to the development of simple command-line utilities, keyb, which echoes bytes generated by keystrokes, and tcolor, which displays ANSI colors on the terminal.
During the COVID lockdown, I decided to learn a bit more about electronics. This eventually led to building an Arduino-based GPS-synchronized clock (hardware and software) of which five generations have since been released.
I also enjoy learning new programming languages when I have time to invest. In doing so, I typically port my RPN compiler and interpreter that was originally written in Scala. The most recent languages were Kotlin and Clojure with ports of the original project here and here, respectively. The next language on deck is Rust.