In June 2011 I launched a serie on my blog called Who is.
This serie took of and I quickly had + 100 people in my backlog to publish. (I did not invited everyone on the list yet, to avoid that people feel bad when they have to wait +6 months before being published)
Anyway, a few weeks back I learned about LeanPub, a service that offers agile publishing. And I created the book Who is agile http://www.leanpub.com/Whoisagile
This book now contains answers from 35 agilists. When you buy it now, you will get updates of the book (more or less on a weekly basis) till we have at least 52 people who answered.
If you don't take our word on it, check out what Johanna Rothman has to say about the book: http://www.jrothman.com/blog/mpd/2012/02/who-is-agile-a-book-on-leanpub.html
Yves Hanoulle & Andrea Chiou