Surveys of dust continuum emission of Galactic star-forming regions have revealed the ubiquity of high column density filamentary structures within molecular clouds, raising the tantalizing possibility that the star formation efficiency is strongly dependent on how these dense structures form and evolve. Here, I will present results from the Green Bank Ammonia Survey (GAS), which provides the kinematic counterpoint to continuum surveys of nearby star-forming regions. GAS has mapped the major star-forming molecular clouds within 500 pc in emission from NH3 and other species. With GAS, we are 1) evaluating the stability of dense gas structures as a function of scale, 2) tracking the dissipation of turbulence and evolution of angular momentum in filaments and cores, and 3) quantitatively testing predictions of models of core and filament formation via mass flows and accretion.