Windows: We've featured distraction-blocking apps before, but Cold Turkey might just be the harshest one of them all. It allows you to block websites and apps at scheduled times.
The fundamental problem with every distraction blocker is that you can usually circumvent them just as easily as you can set them up. Cold Turkey, on the other hand, promises that you can't kill it via the task manager, uninstall it while it's running or change your system time to get around it. While there is a worst-case scenario removal tool, hopefully your lack of self-control won't get that bad.