sometimes, especially if you are like me, your desktop, and other open applications, can cause major distractions to the flow of work, study, or pretty much any task that relies in simple text entry (which is probably why i use textedit over microsoft word)
enter writeroom. this nifty piece of os x software lets you block out all distractions, and leave you with a black screen with oldschool green text. the current version of this fine app is 2.1, and requires os x 10.4 or higher. check it out! sadly, and much to my chagrin, it is no longer freeware, and retails for 24.95 us.
with that said, i poked around the site and found version 1.0, which is a bit more bare in function, but since its pretty bare bones a concept to begin with, it should suffice, and is still completely freeware! download it here.