The article shows the steps that you need to follow to create a simple Hello World portlet using Spring Portlet MVC. It also attempts to explain how Spring Portlet MVC works behind the scenes.
2) Article on developing a Book Catalog portlet using Spring Portlet MVC 3.0 Annotations is now available at DZone: http://books.dzone.com/articles/spring-30-portlet-mvc-part-2
The article shows how to use some of the important annotations to develop a multi-page portlet.
The source code for both the articles is available here, along with source code of the Portlets in Action book: http://code.google.com/p/portletsinaction/downloads/list