we call this feature dynamicity (Roy really loves that word ;)
It will be in the 2.2 release
I am also trying to create a horizontal tab menu. Is there an API to find out what is the current page name?
You could try to look at the JBoss Labs project - we designed our portal layout, so we can access any portlet from any other portlet and created a Navigation menu that lists the available portlets to the user - the positioning of the different windows can be defined in a style sheet by defining regions that will later be used when defining the portlets. I am not exactly sure how helpful that is, but consider the Forge project as an example. (www.labs.jboss.com) - we tried to document as much as we can in the Wiki there.