I can strongly recomend the book "Slack" by Tom Demarco, it is not about Agile, but it is a very good description of some of the practical problems that you as a manager have to deal with, I personally try to live and practice like he write, but it is not easy...
A couple of quotes from the book:
"People under time pressure don't think faster"
"Empowerment always implies transfer of control to the person empowered and out of the hands of the manager."
"Real quality has little to do with defects! Suggest that a real quality program should spend one-ninth or less of it's resources on the defect prevention and removal, and the rest on assuring product uniqueness, usefulness, market impact, change of customer work modes, etc."
"The efficiency-optimized organization recognizes quality as its enemy. That's why many corporate quality programs are really quality reduction programs in disguise..."
"..you can't grow if you can't change at all."
http://www.agilemodeling.com/ A really good place to get ideas, overview, book recomendation etc.
http://deanleffingwell.com/ I have worked with Dean at Nokia, he has some pretty good ideas about scaling Agile in big organisations
http://blog.crisp.se/author/henrikkniberg Henrik Kniberg have created a lot good documentation about Scrum, Kanban and how to get things working in practice, he is a legend in Sweden when talking about Scrum and Kanban.
https://dl.dropbox.com/u/1018963/Articles/HowSpotifyBuildsProducts.pdf a short (10p with pictures) description by Kniberg of how Sportify release, create pilot projects, A/B testing and tweaking products to they become even better.