  We discuss superconductor to insulator and quantum Hall transitions which are
first order in the clean limit. Disorder creates a nearly percolating network
of the minority phase. Electrical transport is dominated by tunneling or
activation through the saddle point junctions, whose typical resistance is
calculated as a function of magnetic field. In the Boltzmann regime, this
approach yields resistivity laws which agree with recent experiments in both
classes of systems. We discuss the origin of dissipation at zero temperature.
