Building IPC Portlets
A technical article that I cowrote with Ed Chen, a Sun Java System Portal Server engineer, Building IPC Portlets for Sun Java System Portal Server 7 With Sun Java Studio Creator 2, is a step-by-step tutorial on how to build JSR 168 portlets that are aware of each other's behavior. The sample application Ed provided illustrates the case well.
Looks like a really neat thing to do! I hope you'll give it a whirl.