SelfControl is a free and open-source application for Mac OS X 10.5 Leopard or later that lets you block your own access to distracting websites, your mail servers, or anything else on the Internet. Just set a period of time to block for, add sites to your blacklist, and click "Start." Until that timer expires, you will be unable to access those sites--even if you restart your computer or delete the application.

Version 2.0.2:

• Fixes major issues with localized copies
• Looks better on OS X Yosemite

Requirements

• OS X 10.7 or later