Scaling Agile Teams Video - Mike Cohn
A good 11minutes summary of how scaling scrum teams is possible, and what are the key steps to create multiple scream teams.
Mike Cohn author of Estimating and Planning User Stories and original signatory of the Agile Manifesto. OnSoftware interviewed Mike Cohn on how it's possible to have a 100 developers become scrum able to deliver software. He uses the microsoft office suite as example for how to split the teams vertically and facilitate communications.