got one better than all this .... on windows go to the location c:\windows\system32\drivers\etc in there is a file called Hosts ... open it with notepad. if you add at the bottom something like
127.0.0.1 facebook.com 127.0.0.1 www.facebook.com
facebook will not load on this computer. rinse and repeat for your friends favorite sites.
127.0.0.1 facebook.com
127.0.0.1 www.facebook.com
facebook will not load on this computer. rinse and repeat for your friends favorite sites.