  We extend a fictitious-cavity approach to calculate the Casimir effect for
cavities bounded by flat anisotropic materials. We calculate the energy, force
and torque in terms only of the optical coefficients of the walls of the
cavity. We calculate the Casimir effect at zero and finite temperature for some
simple systems. As a non trivial application, we calculate the torque between a
semi-infinite anisotropic plate and an anisotropic film. We study the effect of
the film thickness in the torque and find an optimal width that maximizes the
torque.
