Why did you not start on my webpage? All sorts of free and complete JSR-168 tutorials, all free, and nobody ever goes there! Maybe if I started charging people they'd take a bit more interest.
Here's a link to a full multimedia tutorial on developing a JSR-168 Struts portlet:
Full Tutorials, Start to Finish, on Creating a Struts Portlet for Portal Deployment
Here's the link to the completed Struts portlet so you can test it out yourself. It uses the JetSpeed 2.x bridge. You may have to swap the apache portlet bride out for JetSpeed, and put your own portal server bridge in:
Completed Struts Portlet War File for Download and Testing
There is also a tutorial on JSF Portlet Development, along with best practices, and a whole set of JSR168 portlet development tutorials as well.