The Cell Messaging Layer is an extremely fast, MPI-like communication library for clusters of Cell Broadband Engine processors. With it, any Cell synergistic processing element (SPE) can communicate directly with any other SPE, even across a network.
The 8-node PS3 cluster in NCSU. The page contains useful info such as how to use MPI and OpenMP programs on the cluster. It also contains Cell programming tutorials and documents of the Cell and PS3.