You can download example MPI programs as well as MPI benchmarks from http://www-unix.mcs.anl.gov/mpi/. This page is implemented in the form of two frames. Once you have connected click on ``MPICH Home Page'' in the left frame. Then scroll down to ``Demonstrations'', and click on ``Example programs''. The independent address of the page you'll get to is http://www.mcs.anl.gov/mpi/mpich/demo.html. This page lets you download the parallel implementation of the Mandelbrot set calculation.
You will find examples discussed in the ``Using MPI'' books at:
And, of course, you will find annotated examples of MPI programs in these pages too.