Web Sites:

Agile Alliance - community based group.
The Agile Manifesto - the foundation of the Agile model.
Yahoo Agile Software Testing discussion group.
Brian Marick - Agile testing expert.
Gerald M. Weinberg - great thoughts on design & systems thinking.
Goal|Questions|Metric Approach - introduction.
Lisa Crispin - Agile testing expert.
www.satisfice.com - James Bach's website with accumulated testing/quality articles.

Videos:

Competing On The Basis Of Speed by Mary Poppendieck
Getting Things Done by Dave Allen

Presentations:

Focus Your Testing Using the Agile Testing Matrix by Janey Gregory
Various Presentations on Agile Testing by Lisa Crispin