There's a great article in Business Week about Google's innovation champion - Marissa Mayer. The article is called: Managing Google's Idea Factory.
Here's a quote that perfectly describes the primary reason for Google's achievements: "One of the key reasons for Google's success is a belief that good ideas can, and should, come from anywhere. Page and Brin insist that all engineers in the company have one day a week to work on their own pet projects. An ideas mailing list is open to anyone at Google who wants to post a proposal."
Related Links: Google, Innovation