Clusters of today are an important element of mainstream computing. In less than a decade, the "lowly" computer clusters have come to prominence as the most convenient and cost-effective tool for solving complex computational problems. Being able to bring together enough computing cycles together in a pool is one thing, to be able to use these cycles efficiently so that the aggregate power of a cluster can be fully harnessed is another. Research and development effort must continue to explore better strategies to make clusters an even greater tool when facing up to the grandest challenges of this age.