Agile is an umbrella for a number of concepts and approaches that may be used in software development. Here are few links you may find helpful ... The Agile Alliance Extreme Programming: A gentle introduction The Rules and Practices of Extreme Programming The New Methodology Agile Modeling Agile Software Development Scrum Feature Driven Develpment Introduction to Test Driven Develpment Test Driven Develpment TestDriven.Net - A tool for running unit tests within Visual Studio Lean Software Development Visual Studio 2005:MSF for Agile Software Development