Twisted Conch Insults is cool. I wrote the bulk of it almost a year ago, but lately I've been revisiting it with the intent of actually developing some useful software based on it. Since I've never written any major terminal-based apps before, I decided to start with a lot of tiny attempts to get a feel for how things should work.
Most recently, I started tackling the problem of developing a windowing library for insults (Itamar and I paired on most of this one):
There are a couple others in my sandbox for those who are curious. I'm pretty happy with how easy these were. They varied in difficulty from about half an hour of work to about a day's work. Some of the APIs definitely need to be improved (like having a 2-dimensional buffer API for manipulating large areas of the screen, rather than just exposing fundamental terminal operations), but clearly a lot is possible with what already exists. I think I'm going to continue developing the windowing library for now, and then start another round of experiments based on that.