The way the Guardian has implemented Google's 20% is to have Hack Days events twice a year. Today and tomorrow the entire Digital Development department will be spending the day in Shoreditch's Town Hall, where we can do whatever we want for two days. That being said, today's main theme is The Web We Want, so many people will be coding towards that aim.
Picture of a corner of the room while most of the people are in another room playing Human Bingo :)
Also, let me take this opportunity to make my first tweet (well the second one). Had an account for a while, never used it.