What I've used most over the years is his writing about GUI development.
https://defn.io/2019/06/17/racket-gui-saves/ helped me figure out some patterns I had trouble with and got me stuck in using Racket for this purpose in personal projects.
Later he added observables and threading logic, making it even nicer to build GUI, https://defn.io/2021/08/01/ann-gui-easy/ .
The core web development tools in Racket aren't exactly trivial to get started with until one is rather fluent with continuations so I've gained a lot from http-easy and Koyo, https://www.youtube.com/watch?v=DS_0-lqiSVs.
