I'm struggling to meet a writing deadline (how does anybody do this every month for years? Yes, I'm asking you, Roy...) and just found a big helping hand: WriteRoom [1]. It does just what it says it does, expertly well.
As somebody who basically learned to compose prose during my K-12 years while seated at an Apple ][+, a full screen with only a black background and green text is surprisingly supportive of just getting stuff done.
(And there's even a clone for windows called Dark Room [2].)
Now to get back to that piece...
Links:
[1] http://www.hogbaysoftware.com/product/writeroom
[2] http://they.misled.us/dark-room