I have a bunch of tutorials on my website that demonstrate how to develop a HelloWorld portlet using WSAD, and how to do some basic portal administration tasks. They're multimedia, so you can just sit back and watch:
Portal Development and Administration Tutorials There aren't
alot of great books on Portal. This is one of the latest, and deals with JSR-168. JSR-168 is the standard spec:
Building Portals with the Java Portlet API
It's not Head First popular, but it's a start.
Happy Portal!
-Cameron McKenzie