The Wikipedia entry on uncertainty says, "Since the Robertson and Schrödinger relations are for general operators, the relations can be applied to any two observables to obtain specific uncertainty relations. A few of the most common relations found in the literature are given below." It then continues with examples, linear momentum-position, angular momentum orthogonal components, energy-time, the number of electrons in a superconductor and the phase of its Ginzburg–Landau order parameter. I'm curious about other pairs of observables that don't commute. Can someone point me towards a more complete list?