In 1916, Albert Einstein published his famous general theory of relativity, which contains the rules of gravity and provides the basis for modern theories of astrophysics and cosmology. For many years, physicists, astrophysicists, and mathematicians have striven to develop techniques for unlocking the secrets contained in Einstein's theory of gravity; more recently, computational-science research groups have added their expertise to the endeavor. Because the underlying scientific project provides such a demanding and rich system for computational science, techniques developed to solve Einstein's equations will apply immediately to a large family of scientific and engineering problems. The authors have developed a collaborative computational framework that allows remote monitoring and visualization of simulations, at the center of which lies a community code called Cactus. Many researchers in the general scientific computing community have already adopted Cactus, as have numerical relativists and astrophysicists. This past June, an international team of researchers at various sites ran some of the largest such simulations in numerical relativity yet undertaken, using a 256- processor SGI Origin 2000 supercomputer at NCSA.