I did another Whitebook (in dutch). This time the subject is New Features in the APEX 4.0 Early Adopters release.
You can find it at the Whitehorses website.
By the way; besides this personal blog I also publish articles on the blog at the Whitehorses site together with the other Oracle, Java and SOA specialists of the company. These blogs are in english. A direct link to the list of my blogs is in my profile.