Perhaps you've seen a mac colleagues with brilliant concentration. They aren't succumbing to the usual temptations of facebook and the like, and you just wonder, how do they have this superhuman power? To let the cat out of the bag, they very likely have SelfControl.
This is no longer the case for Windows, with Cold Turkey.
Just like the Self Control (you can see our write up here), Cold Turkey allows you to block websites for as long as you like, without any way to reverse it until the time has expired.
Interesting, the app is 'donationware.' Meaning that you, the user, pays an amount that you believe is worthwhile. This is not a foreign concept to the world of computer programs, but it says something about the developer - they're putting their trust and confidence in you to provide them with enough money to live. So do consider paying something, but if you can't you're still able to go Cold Turkey.