I sometimes use JDarkroom for writing.  It blanks out the screen, giving only monospaced text, letting you focus on words (not formatting, the clock, the weather, email, surfing, or blog reading).

But when I need to think, turning off the computer entirely and writing on paper seems to work best (I like the large squared Moleskine notebooks).  It goes everywhere, boots instantly, and never crashes.  Because my writing bandwidth is much lower than my typing bandwidth, I focus more on thoughts than words.

For creative thinking, I also find it helps to shake up my surroundings.  I like leaving the office and going to a restaurant, coffee shop, library, museum, etc.  I’ve even made excellent “think time” out of waiting at the dr’s office, waiting to pick up the car with new tires, etc.

Try scheduling some notebook time.