We will present recent nonlinear optical experiments on organic microcavities in the strong-light matter coupling regime. In this regime, new quasiparticles called polaritons are typically introduced to describe the hybrid exciton-photon state. When this occurs, the photon inherits the intrinsic nonlinearity of the exciton and furthermore, the nonlinearity is resonantly enhanced. We will use this fact to demonstrate room-temperature superfluidity of exciton-polaritons. In this regime, a laser is used to create a superfluid flow of light, which can flow past defects without scattering. Using interferometric imaging, we can clearly observe the vanishing of turbulance and vortex formation in the superfluid regime. This confirms a 20 year old prediction on the superfluid flow of light by Chiao et al. Then, we will show that infrared organic polaritons can be used to generate efficient and tunable third-harmonic generation throughout the visible spectrum and we will give some perspective on further excitonic effects that could potentially be harnessed using polaritons.