Well, before we jump deeper into the application, please let me quote the definition of Markdown taken from Wikipedia:

Markdown is a lightweight markup language, originally created by John Gruber and Aaron Swartz allowing people "to write using an easy-to-read, easy-to-write plain text format, then convert it to structurally valid XHTML (or HTML)". The language takes many cues from existing conventions for marking up plain text in email.
Just like another markup languages, we can create Markdown with ordinary text editor such as Gedit or Kate. But Uberwriter gives you some advantages when writing or editing Markdown markup language.

Some of UberWriter features:
  • Beautiful, simple, and clutter-free editor
  • Has fullscreen and focus mode
  • Inline Markdown Highlighting
  • Export markdown to PDF, RTF, and HTML using Pandoc library
  • Syntax highlighting and math in HTML and PDF.

Install UberWriter on Ubuntu
Ubuntu users can install it easily by running the following command:
  • sudo add-apt-repository ppa:w-vollprecht/ppa
  • sudo apt-get update
  • sudo apt-get install uberwriter
UberWriter is in early development stage. Many features will be added in the next release:
  • drag-and-drop link and image inserting
  • copy as raw html
  • import documents other than markdown
  • ubuntu one integration

UberWriter screencast:

UberWriter website.