Agile Development in a nutshell

On the site of the product Version One (one of the leading project planning and management tool designed specifically for agile software development), you can find a well structured introduction to Agile developments.

It covers briefly but sharply many points such as overviews of the different methodologies,  some project management practices, and some programmer practices.

http://www.versionone.com/Resources/AgileDevelopment.asp