The most polished and useful program I've made for personal use is an emacs minor mode that lets you scroll down top lines in a file. I was tired of having to always look all the way at the top of the editor window to read the top lines of a file or small files.

https://github.com/trevorpogue/topspace

I also made a Python tree data structure library to easily parse and read tree structures which I actively use in other personal projects.

https://github.com/trevorpogue/sections