It is now possible to generate terahertz (THz) pulses with sufficient energy and field amplitude to enable versatile applications in THz nonlinear optics and spectroscopy. In addition, THz waveform shaping at high intensities promises wide ranging new capabilities in THz coherent control. We review recent progress in generation of high-power THz phonon-polariton waves in lithium niobate that can be coupled into free space THz radiation. A ldquopolaritonicsrdquo toolset for control and processing of the THz waves is also reviewed briefly. Recent demonstrations of THz nonlinear optics and spectroscopy are then presented.