The Atacama Cosmology Telescope (ACT) is a six-meter telescope on the Atacama plateau, Chile that was built to characterize the cosmic microwave background (CMB) with arcminute resolution. Since 2008 ACT has been used to measure the temperature anisotropies in the CMB in three bands between 140 – 300 GHz with the largest arrays of transition-edge sensor (TES) bolometers ever fielded for CMB observations. Two of the primary science objectives for these measurements are: detecting galaxy clusters via the Sunyaev-Zel’dovich effect, which can be used to study the dark energy equation of state when combined with optical redshifts, and measuring the CMB power spectrum at high multipoles to improve constraints on cosmological parameters. Analysis of these data is underway and preliminary results will be presented. A new receiver for ACT is under development that will add polarization sensitivity to the telescope in addition to having ~5x the temperature sensitivity of the current receiver. With these improvements we will pursue a number of additional science objectives, including: multiple constraints on the sum of the neutrino masses with ~0.06 eV accuracy, looking for deviations from the standard cosmological model, “delensing” the gravitational lensing of the CMB, and a variety of cross-correlation studies by combining our data with the next generation BOSS survey from SDSS. These improvements are enabled by a new detector focal plane technology under development at NIST that comprises large arrays of feedhorn coupled TES polarimeters. We will described the design of the new receiver including the coupling optics, detector arrays, readout, and 0.1 K cryogenics as well as our projected timeline for deployment.