I have several projects that I develop just for myself.

One is a command line based database browser/editor. PhpMyAdmin for the terminal, so to say. I do all my database work inside of this editor. The terminal is just so much faster. And has many benefits like that I can use it over ssh and in containers.

Another one I started recently and already use is a terminal based project planner that is completely file based. Each task is a text file.

One that I am currently planning is an ActivityPub client. Like Mastodon but way way leaner. For now, I am basically playing with ActivityPub requests on the command line. Later, I will add a Python web interface on top of it.