While in my final years at university I thought it was interesting to learn about continuous integration and build tools. Since I was doing assignments in programming languages that have these documentation tools, I set up the documentation to be automatically build every time I pushed to the respective repository. In some ways this is a bit of a graveyard for old code, but it remains as an interesting reminder to myself that I did this.
Nowadays, I tend to write a lot of code in Python and Go. I found that Python does not really have automated documentation tools (and if it did I could never find it) - I found it silly to have to rewrite things into .rst files. Go on the other hand has nicer tools and a service that hosts documentation for free; so that's what I use now.