The Parallel Java library (see http://www.cs.rit.edu/~ark/pj.shtml) is a very nice 100% Java library that can be used for this. The book from the author is also a nice text for Java programmers.
I am so fond of this, that I plan to add Model Elements to EJS that will make it easy for an EJS author to parallelize a model in a shared memory multiprocessor computer. (The library also supports small clusters.)
I also plan to use the examples from Kaminsky's book (see the Web page above) to create the corresponding EJS examples.
When will this be ready? I can't promise it, because the term hasn't finished yet in Spain. But I want to work on this before the summer and maybe finish it during August.
Ok. Here they are. The latest EJS has brand new Model elements based on the Parallel Java library that allow you to create nice parallel algorithms. The source code examples contain a number of examples taken from the book "Building Parallel Programs" by Alan Kaminsky. These are tools for multicore shared-memory computers. I have tried the examples with a 12 cores computer and the result is superb! The examples are in users/murcia/fem/demos/ParallelElements