Ur-Scheme: A self-hosting compiler from a subset of R5RS to x86 https://canonical.org/~kragen/sw/urscheme/ (interesting and a great list of related projects!)
Related Posts
For hobby projects, I really like software where I can do small features or tweaks. Sometimes I don't have time for anything more substantial.
Website projects are great for this. Are there other areas?
I've started keeping a list of particularly interesting bugs and patches that I've worked on: https://github.com/Wilfred/interesting-code
The time that I once removed *a single closing paren* in Emacs is still my favourite.
The most common selling point I hear for Nix is having a list of all the packages you need.
On a traditional Linux distro, I just install things and forget about them. A curated, commented list would certainly be handy when I have a new system.