Go Fucking Work - Website blocker so you can get back to your fucking work
BlockParty - Real-time voice chat rooms from the creators of turntable.fm
Focus - New Tab page that gives you a moment of calm and inspires you to be more productive.
Secateur - Use Secateur if you want to temporarily or permanently block or mute (or both block and mute) a Twitter account and all its followers.
Block Facebook - Chrome Extension that protects your privacy by blocking FB
Boyfairy - Your opportunity to educate right before you block someone.