Sonatype is happy to be helping the Hudson community with our support of the Hudson book.
The goal of the Hudson book is to be the authoritative source of documentation for Hudson users. We expect it to be available soon. Stay tuned to this blog for updates on the availability of the Hudson book.
For the perspective of one of the key contributors to the project, see Manfred Moser's recent blog post, "Hudson - Book, Changes, and Community."
Since the [Hudson] project lives on github it is pretty easy to follow the usual clone, branch, hack, commit, pull request sort of flow and thanks to Maven the build is as easy as .. surprise .. mvn clean install.
Read more of Manfred's blog on Simpligility.