Darkcopy

"DarkCopy is incredibly simple; it's a Web-based text editor that you can use to block out the rest of the world while you write. You can use the text editor from within the DarkCopy homepage, but its real usefulness is revealed when you click to make the tool full-screen. A new window opens that takes up your entire display. The window is completely black, save for a blinking green cursor. That's all there is to it: get to work."

http://www.appscout.com/2008/04/darkcopy_helps_you_write_witho.php

http://darkcopy.com/