Nonlinear photonic crystals are materials in which the second order susceptibility is modulated. These structures are often used in nonlinear optics applications for compensating the phase mismatch between interacting waves. The progress in techniques of modulating the nonlinearity enables to explore new applications, based on all-optical control of the phase, amplitude and polarization of the nonlinearly generated waves. This enables the realization of functional nonlinear optical devices, such as nonlinear lenses, switches, polarization rotators, deflectors and beam shapers. Here we will discuss in detail two applications that are enabled by specially designed nonlinear photonic crystals: All optical polarization switching, and the generation, nonlinear mixing and manipulation of accelerating Airy beams.