  We review current progress in the functional renormalization group treatment
of disordered systems. After an elementary introduction into the phenomenology,
we show why in the context of disordered systems a functional renormalization
group treatment is necessary, contrary to pure systems, where renormalization
of a single coupling constant is sufficient. This leads to a disorder
distribution, which after a finite renomalization becomes non-analytic, thus
overcoming the predictions of the seemingly exact dimensional reduction. We
discuss, how a renormalizable field theory can be constructed, even beyond
1-loop order. We then discuss an elastic manifold imbedded in N dimensions, and
give the exact solution for N -> oo. This is compared to predictions of the
Gaussian replica variational ansatz, using replica symmetry breaking. We
finally discuss depinning, both isotropic and anisotropic, and the scaling
function for the width distribution of an interface.
