The Definitive Guide to Plone was published by Apress, 2004 for Plone 2.0

Unsupported
Errata
Links
Scripts
Software

Please note: the book is under a creative commons license and has been designed to be something that will adapt and grow with Plone. Almost entire book is available in CVS on sourceforge. If you would like to help out or contribute then that's a great place to go.