I wrote a paper for the 2007 PMI Global Congress in Atlanta on Agile Transition.  Part of the paper covers the Agile Manifesto.  As I began researching and writing about it, I found that I had gaps in the historical data on the web.  I was fortunate enough to interview Jim Highsmith, Ward Cunningham and Ken Schwaber via telephone to get a better understanding of how the Agile Manifesto came about.