It's worth noting that Hacker News has an anti-procrastination feature: set the "noprocrast" option in your profile to "yes", and then it will time-limit your v

It's worth noting that Hacker News has an anti-procrastination feature: set the "noprocrast" option in your profile to "yes", and then it will time-limit your visits to "maxvisit" in minutes, and block you for the "minaway" period. I don't know of any other site that does this. It's a very cool thing for Y Combinator to have done.