Our WebCenter 11g book has been out a few weeks and I have heard some good reviews from people who have picked it up. This version 1 book will quickly get you started with WebCenter 11g, providing you step-by-step screenshots on creating your environment followed by a Hello World web service that is exposed to the web as a WebCenter portlet among other common business scenarios you may need to accomplish.
You can buy the book directly from the publisher, Packt Publishing at: https://www.packtpub.com/web-2-0-solutions-with-oracle-webcenter-11g/book.