- This book is a little outdated but it is really good at getting you started using Plone and understanding the architecture. I have heard that Plone Content Management Essentials is also a good getting started book but I have not read it.
- When you are starting to get serious about building websites in Plone, you should read Plone Live. This book discusses how to do Filesystem based development and packaging components as products. It is also regularly updated, which maybe all books out open source should be.
- At the point where you start writing Python code that is more advanced than what you copy of the web, buy Dive Into Python. This will walk you through some nicely written Python code and explain how it works.
- Although seriously out of date and out of print, The Zope Bible is still the best book on the Zope 2.x series. Unfortunately, the newer Zope books are all on Zope 3.x which is less relevant to your average Plone developer.
- File System Plone Skin. The plone.org site looks nice but in case you don't want you site to look exactly like it, follow this tutorial. Don't dump stuff into the custom folder in the ZMI. Do it the right way.
- Running Plone behind Apache. If you are going to expose your Plone site on the big Internet, you should run it behind Apache. Here is the most detailed description of how to do it.
- CacheFu and Squid. If you think your site might get some heavy traffic. Run CacheFu.
- Zope/ZEO Configuration. If you think that someone would care if your Zope instance crashed, or if you want more performance, set up a ZEO configuration.
Hire a Teacher
Joel Burton runs a great program called Plone Bootcamps. It is amazingly affordable if you have a big group. Nate Aune from Jazkarta is an excellent source for more customized training.