The South Pole Telescope (SPT) performed a five-year survey from 2007 to 2011, mapping 2500 square degrees of the mm-wave sky with exquisite sensitivity and angular resolution. I will discuss the discovery of hundreds of new massive galaxy clusters through the Sunyaev-Zel'Dovich (SZ) effect. These clusters form a mass-limited, redshift independent sample with a well-understood selection function. Comparison to theoretical abundance yields strong cosmological constraints, limited only by the unknown scaling relation between the SZ effect and cluster mass. In order to improve our knowledge of cluster scaling relations, we have embarked on a multi-wavelength follow up campaign. I will describe the most recent results and show projections for SPT cluster cosmology in the near future.