According to the EJB spec, if you want asynchronuos processing you should use message beans.
In my case I need to process a lot data using the replicated workers pattern and the objects used by the workers are very granular, and reference other objects so it's not appropiate to pass them as messages. The JMS overhead would be considerable.
Are you guys aware of any framework for asynchronous processing integrated with J2EE? In its simplest form this could be just a thread pool that fits nicely in the J2EE architecture.
You might have to take a look at 'spring framework' by Rod Johnson. It's getting famous these days.