If you use a mac check out http://macfreedom.com/ or http://anti-social.cc/ I use freedom every time I have work in front of me that I want solid time to complete and I can't trust myself not to get distracted down some rabbit hole. It sounds stupid at first but two things it does for you over just unplugging from the network is that 1) you can still communicate with your local network/VPN and 2) you can't get back online without restarting your machine.