Must Read

The New Methodology by Martin Fowler

Definitions of Agile Software Development

Wikipedia Definition
c2.com Definition

Websites

Agile Alliance	www.agilealliance.org
Agile Manifesto	www.agilemanifesto.org
Agile Modeling	www.agilemodeling.com
Crystal	alistair.cockburn.us/crystal/crystal.html
DSDM	www.dsdm.org
Extreme Programming	www.xprogramming.com www.extremeprogramming.org www.xp123.com www.industrialxp.org
Feature-Driven Development (FDD)	www.featuredrivendevelopment.com
Lean Development	www.poppendieck.com/index.htm
Scrum	www.controlchaos.com www.mountaingoatsoftware.com/scrum www.scrumalliance.com

Books on Agile Development

Agile Software Development

Cockburn, Alistair.	Agile Software Development. Boston: Addison-Wesley, 2002.
Highsmith, Jim.	Agile Software Development Ecosystems. Boston: Addison-Wesley, 2002.
Martin, Robert.	Agile Software Development, Principles, Patterns, and Practices. Saddle River, NJ: Prentice Hall, 2002.

Agile Development Management

Cohn, Mike.	Agile Estimating and Planning. Prentice Hall, 2005.
Anderson, David J.	Agile Management for Software Engineering - Applying the Theory of Constraints for Business Results. Upper Saddle River, NJ: Prentice Hall, 2004.
Highsmith, Jim.	Agile Project Management: Creating Innovative Products. Pearson Education, 2004.
Larman, Craig.	Agile and Iterative Development: A Manager's Guide. Boston: Addison-Wesley, 2003.

Crystal

Cockburn, Alistair.

Crystal Clear: A Human Powered Methodology for Small Teams. Boston: Addison-Wesley, 2004.

DSDM

DSDM Consortium, et al.

DSDM: Business Focused Development, Second Edition. Boston: Addison-Wesley, 2003.

Extreme Programming

Beck, Kent.	Extreme Programming Explained: Embrace Change. Boston: Addison-Wesley, 2000.
Beck, Kent, Martin Fowler.	Planning Extreme Programming. Boston: Addison-Wesley, 2000.
Cohn, Mike.	User Stories Applied: For Agile Software Development. Boston: Addison-Wesley, 2004.
Jeffries, Ron, Ann Anderson and Chet Hendrickson.	Extreme Programming Installed. Boston: Addison-Wesley, 2001

Feature-Driven Development (FDD)

Palmer, Stephen, and Felsing, John M.

A Practical Guide to Feature-Driven Development. Prentice-Hall, 2002.

Lean Development

Poppendieck, Mary, and Poppendieck, Tom.

Lean Software Development: An Agile Toolkit for Software Development Managers. Boston: Addison-Wesley.

Scrum

Schwaber, Ken, Mike Beedle.	Agile Software Development with Scrum. Upper Saddle River, NJ: Prentice Hall, 2002.
Schwaber, Ken.	Agile Project Management with Scrum. Redmond, WA: Microsoft Press, 2004.