The central problem in Polycrystal Plasticity is concerned with predicting the macroscopic response of a polycrystalline material given the yield set of the basic crystal and some additional information on the shapes and orientations of the grains (texture). I will discuss a general strategy for the resolution of this problem with an emphasis on several model cases. The new approach allows us to characterize the effective yield set of the polycrystal by means of certain variational principles in L-infinity. The corresponding supremal functionals are obtained as Gamma-limits of power-law functionals acting on fields subject to constant rank differential constraints.