Temporarily blocks sites you specify so you can get some work done.
This extension aims to keep you productive by blocking access to sites that you specify. It's easy to add and remove sites to the list, as well as enabling/disabling the blocking feature.
This extension has been released as open source. See the website link for details and the source code.
As of version 1.0.2, the issue of the extension not working without a restart of chrome should be resolved.