Uberwriter is a GTK+ based distraction free Markdown editor, mainly developed by Wolf Vollprecht. It uses pandoc as backend for markdown parsing and offers a very clean and sleek user interface.
With UberWriter it’s simple to write beautiful documents in Markdown.
Features include 'focus mode' that highlights your last sentence and gives you a typewriter-esque feel, out of the box spellcheck, and a very clean interface. There is a fullscreen mode which gives you a whole, white page. And the best: Inline Markdown highlighting. It’s a remarkable simple idea but works very well. More Info »
Through pandoc, it is currently possible to export from UberWriter to pdf, html and rtf.
A bonus pandoc feature: Syntax highlighting and math in HTML and pdf.