I run a fork of geminid. There are at least two codebases using that name: one in C, and one in Chicken Scheme. I'm using the Scheme server. The original program, without my modifications, can be cloned from git://upyum.com/geminid.
One of my changes adds on-the-fly conversion from markdown to gemtext, using Idiomdrottning's 7off.
If I want to post in Markdown, and I usually do, I write a Markdown file locally and save it as index.md in a directory named for the URI slug of the post. If you want to read this post as gemtext, you can visit gemini://the-brannons.com/gemini-stack/index.gmi. If you'd rather see it as markdown for some reason, you can visit gemini://the-brannons.com/gemini-stack/index.md.
At some point, I'm thinking about adding some features, like Titan support. Mainly it could be for uploading posts. In an ideal world, I wouldn't need SSH access to my Gemini server just to write a blog post.
I need to get around to publishing my code.
gemini://the-brannons.com/gemini-stack/index.gmi
gemini://the-brannons.com/gemini-stack/index.md