Books

Extreme programming explained Extreme Programming Explained: Embrace Change 1st edition. Now out of print get it used for a couple dollars. This is still a worth while read if you are new to XP.

Extreme Programming Installed Extreme Programming Installed. This book covers specific XP practices. This book teaches how to program XP style.

Succeeding with Agile Mike Cohn's new book. Solutions to most problems transitioning to Agility. Written for Scrum, but good for any Agile team.

Planning XP Planning Extreme Programming is all about release planning and iteration planning.

Extreme Programming Playing to Win Extreme Programming Applied: Playing to Win Experiences from pioneers in applying XP.

Agile Extimating and Planning Agile Estimating and Planning.

Agile Testing Lisa Crispin's book on Agile Testing.

Books

Extreme Programming Explained Extreme Programming Explained: Embrace Change 2nd edition. This is an advanced book on XP. How to change XP to fit your specific project and values.

Pocket guide Pocket Guide.

Test Driven Development Test Driven Development is the art of creating code by writing the test first.

Working with Legacy Code A book of good advice for working with code that has no unit tests and resists testing.

Refactoring Refactoring Improving the Design of Existing Code. The first authoritative volume on refactoring. This book teaches you how to refactor and why.

User Stories Applied User Stories Applied.