I was just randomly broswing and reading IBM websphere portal tehnotes, and came across with an excellent new thing where in we can integrate Rich Internet Applications controls into WebSphere Portal.
Here RIA controls referes to like Flex controls that we can integrate into portlets that are based on JSR286 specification.
Read out in detailed article here
Integrating Rich Internet application (RIA) controls into IBM WebSphere Portal
If you look at the Resources section at the end of this article, you will also find very good articles specially on how to integrate Flex, Ajax and JSR286 portlets.
Thanks to Adam and Peter for such a wonderful article.