Here's another free tool for writing, Sadhana Ganapathiraju's Blockwriter (Windows only), inspired by Khoi Vinh's still-hypothetical Mac program of the same name.
Blockwriter offers an extremely simple (some will say limited) writing environment: no deleting by backspacing; no cut, copy, or paste; no options to change window size or font size. The delete key replaces letters with bullets. There is no option to print, but Control-S will save what you've written as a text file. If you click to close the program before saving, there's no prompt asking if you'd like to save your work. The most enticing feature, for me, is the dark screen that covers the desktop (and any other open windows) as long as Blockwriter is running.
Blockwriter is alpha software, with at least two possibly annoying problems. One: if you minimize the Blockwriter window, everything remains dark, with no way to get the program back (it's necessary to call up the Task Manager -- Control-Alt-Delete -- to close the program). Another problem (explained on the programmer's website) involves involuntary auto-scrolling.
Blockwriter might be a little extreme for ordinary writing (I'm always fixing typos on the go, so I miss the backspace key), but it might be just the ticket for someone who needs to eliminate all distractions and get something said. Blockwriter offers a writing environment that manages to be both austere and inviting.
Update, January 22, 2007: A new version of the program fixes the two problems described above. Thanks, Sadhana!
Blockwriter (requires .NET 2.0 from Microsoft)
Blockwriter (Khoi Vinh's program proposal)