P2P-MPI
P2P-MPI is both an MPJ implementation and a middleware for the management of computing resources. Similar to the idea of sharing files through a P2P system, P2P-MPI lets its users share their CPU and access others’ CPUs. P2P-MPI is oriented to desktop grids: it is runnable as a simple user (no root privilege needed) and provides a transparent mechanism for fault-tolerance through replication of processes.
See dedicated site for more information : www.p2pmpi.org