I wish I had an API for updating my Jekyll blog, which is hosted on GitHub pages.
I don't mind using Git to update it, but it would be cool if I didn't have to.
I made a proof of concept version in January 2014, which I wrote a blog post about. That version is browseable at this tag. I'm sort of tempted to make this a more generally useful thing (that version would have only worked for me).
Here's the vision: https://github.com/maxjacobson/jekyll_api/issues/1