"Focus is concerned with input, not output. It is not about turning one particular thing “on” but about turning other distractions off."
~ James Shelley from Focus: Controlling the Inputs of Social Media
For those of you/us looking for a little help "turning it off" here's two simple apps you can use to render your computer useless (save for the actual program you're wanting to concentrate on).
1. Steve Lambert's Self Control allows you to create a "blacklist" of programs etc and will lock them down for a pre-determined amount of time.
2. Similarly, Workabit doesn't let you pick and choose which programs to shut down, but instead locks everything but the program you're currently working in.
Of course, there's also this thing called the "power button" which works wonders in driving one toward a pen and paper.