I will discuss quantum metrology experiments in our lab using large ensembles of cold, trapped atoms and cavity QED. The first portion of the talk will describe conditional spin squeezing of the clock transition of a million Rb atoms, achieved by utilizing the vacuum Rabi splitting as a collective QND meter. The second portion of the talk will describe a Raman laser that operates deep into the superradiant or bad-cavity regime. The system is demonstrated to operate with <1 intracavity photon and with an effective excited state decay linewidth <1 Hz. This model system demonstrates key physics for future active optical clocks (similar to masers) that may achieve frequency linewidths approaching 1 mHz due to reduced sensitivity to thermal mirror noise.