LAM (Local Area Multicomputer) is an MPI programming environment and
development system for heterogeneous computers on a network.  With LAM,
a dedicated cluster or an existing network computing infrastructure can act
as one parallel computer solving one problem. 

LAM features extensive debugging support in the application development cycle
and peak performance for production applications.  LAM features a full
implementation of the MPI communication standard.

WWW: http://www.lam-mpi.org/