Once upon a time computers only displayed text in a soothing shade of green or amber. Then came graphical interfaces will colors, bells, whistles, and all sorts of distractions. Several enterprising developers with retro sensibilities now offer "Distraction-free" editors. While no longer restricting you to green characters, these editors give you nothing but a blank screen and your words. Having an editor in which I could focus entirely on my words has helped me use my limited writing time well.
I use a Windows package called Write Monkey [http://writemonkey.com/]. There are similar packages for the Mac.
Of course, life is ever as simple as it should be and Write Monkey has its drawbacks, most of which come back to the fact that it is a text editor, not a word processor. This means that you get plain double quotes instead of the nice opening and closing quotes that Word supplies as you type. Also, Write Monkey doesn't convert a pair of dashes into an em-dash (again, like Word). I turned this liability into a feature: after writing about a chapter with Write Monkey, I import the text into Word and use the fact that quotes and em-dashes need to be corrected as an excuse to edit the new material.
I have a longer note about Write Monkey on my blog at http://blog.derenhansen.com/2010/04/writing-technology-green-screens.html
Deren, I love the idea of a distraction-free window. It would work really well with the "unplug" hours I've been doing. I think I'll try combining the two. I'm bound to get some writing done then!