Extreme Programming was created by Kent Beck, Ward Cunningham, and Ron Jeffries during their work on the Chrysler Comprehensive Compensation System (C3) payroll project. Kent Beck became the C3 project leader in March 1996 and began to refine the development methodology used on the project. Kent Beck wrote a book on the methodology, and in October 1999, Extreme Programming Explained was published.
Extreme Programming, or XP, is a lightweight discipline of software development based on principles of simplicity, communication, feedback, and courage. XP is designed for use with small teams who need to develop software quickly in an environment of rapidly-changing requirements.
Extreme Programming Wiki
Extreme Programming: A gentle introduction.
What is Extreme Programming? by Ron Jeffries
When should Extreme Programming be Used?
Oracle and Extreme Programming