Sometimes for fun, I think of an odd idea for a webpage and I make it. Using CSS, HTML, and javascript. It can be really fun just to make silly webpages and have your friends see it.
Orbital simulator, to assist in building a fictional solar system (for a sci-fi fantasy story that I’m writing).
I also made a series of pages that served as a digital puzzle / scavenger hunt for my wife, as a gift on our first Valentine’s Day before we got married. (That one I might keep personal between her and me.)
A little RPG game in JavaScript called Ralk Journey, based on material I created in my childhood
An archive website showcasing the Minecraft worlds on a friend’s old server from our college days.
I made the commemorative website for him for his birthday this year. I got some decent Desktop backgrounds out of this project too! (Visible on the “Art” page.)