The first one, C-Linda, is available at a cost. The other packages are public domain. All run on a wide variety of platforms. MPI is a standard that encompasses many of the features of P4 and PVM, and the some. It is a very large package.
Simulators are also available that run on a single platform.
While convenient, real timing studies are not possible. These too run on a variety of platforms, except where noted. The package is free. Runs on IBM PC's or compatibles. A PRAM simulator.