There are three very informative and inspirational sources of information that I recommend to all teams starting with agile or looking for some extra motivation:
1. Henrik Kniberg’s “Scrum and XP from the Trenches” (http://www.infoq.com/minibooks/scrum-xp-from-the-trenches). Available as free PDF after registration.
Extremely good source of information, tips and tricks, pitfalls and how to avoid them, planning ans estimation techniques. Henrik is speaking out of his own experience, which makes this book extremely valuable. You can read this book in just a few hours.
2.Ken Schwaber’s talk “Scrum et al.” at Google
Ken is is a founder of the Agile Alliance and Scrum Alliance, and signatory to the Agile Manifesto.
One hour of valuable information – and hopefully after watching this video you will not try to adopt agile and scrum where it is going to do more harm than good.
3. Agile Manifesto (http://agilemanifesto.org/)
Print it out and pin it to the wall, so you can see it every day. Doing Agile and Scrum “by the book” never works – there’s no book that can tell you what the process should be. Not only because each team has its unique qualities and each organisation has its own constraints, but most importantly because agile is all about changing the process with every iteration – improving it and adopting to the changing reality.