The newest piece is 'PicoContainer-Web Remoting' (PWR). Ideas that were pioneered in Waffle some years ago have been reborn as a separate framework for directly calling into scoped components over HTTP. Objects essentially get URLs, including their method names. The results of method calls are turned into JSON transparently. Parameters to methods are matched by parameter name. Read more about it here
You can use it on its own, or with Struts 1/2, or WebWork 1/2
There are many similarities to recent editions of Spring MVC, and Direct Web Remoting (DWR) of course.