There are always simple tools for simple needs which will give you nothing more and nothing less. The tools that I am going to mention both functions the same way but has some differences.
The Write Room is a Mac OSX application and developed by Hog Bay Software that offers a distraction free writing experience. It is a simple writing tool and nothing more. It is not a full function word processor so don’t expect tabs and tables in the application. Write Room features Full-screen, Document based auto-saved, Distraction free features: which hides the menubar and wordcount, Retro Cursors and Standalone or Edit-in feature which will compliment another program if it is compatible. You can download a free fifteen (15) day trial in their website or get the full version for twenty five ($25) dollars.
Dark Copy is an online Write Room clone which is not limited to a Mac OS-X operating system. All you need is a browser and you can enjoy a distraction free writing experience. No need to download and the service is free.
DarkCopy is for anyone who enjoys the simplicity of a typewriter, and wants to increase productivity by focusing only on writing. It was created as a free, web-based clone of WriteRoom.
The difference between the two apps is of course the price tag and some key features in the free version. There are key features in WriteRoom which is not available in DarkCopy. The auto save feature is I think most essential in any digital writing application. But who am I to argue with a free web application which serves its purpose of creating a different writing experience in this cluttered digital age. Just hit the save button once in a while to prevent data loss (or is it going to be another distraction?).