My idea of the perfect system would be something hosted that would allow me to have a shared folder in Dropbox, Google Drive or something like that. It would have two folders, drafts and posts, and putting a markdown file in either would publish it as a draft or a post.

I've looked at a few static site generators, but there are some dynamic things I want to do, so, for now, my own, custom-built blogging engine (http://stavros.io for the curious) is what works best for me.