  Novel optical phenomena, including electromagnetically induced transparency,
slow light, superluminal light propagation, have recently been demonstrated in
diverse physical implementations. These phenomena are challenging to realize in
practical systems because they require quantum coherence as well as careful
preparation and control of prescribed quantum states. Here we present a unified
approach to engineering optical materials that exhibit these phenomena by using
mixtures of active and passive optical materials at frequencies near their
resonances. Our approach does not depend on quantum coherence and can realize
large and small (much less than 1) indices of refraction and negative
permittivity ($\epsilon<0$), normal and anomalous dispersion, all while
maintaining transparency.
