A Gopher browser with built in markdown rendering? (That's the simplest project on my someday/maybe list.)
It's an internet protocol similar to ftp or http, but much simpler than http, and more suited to browsing than simple FTP.
Designed for serving plaintext files, mostly.
(Sorry, typo in the original. Gopher is better for browsing than FTP. Http brings a lot to the table, even though it hides most of those things behind lots of extra complexity.)
A social network for the 19A0s.