Independent Developer Projects in the Workplace?

An anonymous reader asks: "My company wants to increase creativity and innovation, we our thinking of implementing a Google like policy of 20% of your time for independent projects but I can't find any details on how Google actually implements this. I am curious how they divvy up their time (1 day a week or 1 week a month)? How do you keep your real project from impacting it? At what point are the projects reviewed? Has anybody experienced other successful ways to stimulate creativity at their workplace?"