One of the original hubs of XP discussion on the web. This site is a Wiki, letting any and all visitors take part.

A primary XP portal, run by Ron Jeffries, the original XP coach, and one of it's most vocal and prolific advocates. Be sure to check out the online journal.

This site is by Don Wells, a member of the C3 team where XP was conceived. Don has done a great job providing A Gentle Introduction to XP (his words). He's also diagrammed XP very nicely. This site will reward your exploration.

ObjectMentor has long been a powerful force in XP. Their roster includes names like Bob Martin, Ron Jeffries, & Mike Feathers. Their site has a collection of XP papers, and they host and maintain a number of XP-related sites. Also check out XP Immersion, their week-long XP training course (which we at Adaption highly recommend).

This is the place to get everything related to jUnit, the very powerful automated unit testing framework, including downloads of the latest version and extensions. Hosted by ObjectMentor.

Go here to read articles, anecdotes, and studies on pair programming. Hosted by ObjectMentor.

This is Martin Fowler's site where he "tries to collect as much information on refactoring as he can keep up with".

XP123

This is William Wake's site which includes his great XPlorations series or essays that lead to the book XP Explored.