  Galaxy clusters furnish extremely rich information on the contents and
structure of our universe. The potential of galaxy cluster studies to constrain
dark energy, for example, motivates a number of ambitious cluster surveys.
Among these, surveys based on the Sunyaev-Zel'dovich (SZ) effect are
particularly powerful for their ability to cleanly select clusters out to
redshifts z>1. Now poised to begin surveying substantial areas of sky,
dedicated interferometers, bolometer cameras and the Planck satellite will soon
produce large cluster catalogs that will provide a precise measure of the
cosmic expansion rate over a range of redshifts and precipitate a new
understanding of structure and galaxy formation. I review the science potential
of these surveys and examine some issues of SZ cluster catalog construction.
