Defining Agile
As Agile delivery is an umbrella term being hijacked left, right and centre (who would admit to being non-agile?), I came across a great definition from one of it’s primary proponents;
“My definition is that you accept input from reality, and you respond to it” (Kent Beck)
Some great agile links;
http://www.agilemanifesto.org/ – Homepage of the original Agile Manifesto, including the 12 principles
http://www.devagile.com/ – Central site, with agile links, articles, discussion etc.
http://www.waterfallmanifesto.org/ – Joke site supporting Waterfall delivery
http://www.infoq.com/ – Vast array of Agile resources
http://agile-commentary.blogspot.com/ – Agile commentary blog

I also have a blog post on resources for agile or where to start. The first thing I would put on the list though would be the infoq website.
Thanks for those links Kevin, two great sites – much appreciated!