  We review some models of granular materials fluidized by means of external
forces such as: random homogeneous forcing with damping, vibrating plates, flow
in an inclined channel and flow in a double well potential. All these systems
show the presence of density correlations and non-Gaussian velocity
distributions. These models are useful to understand the role of a kinetically
defined ``temperature'' (in this case the so-called {\em granular temperature})
in a non-equilibrium stationary state. In the homogeneously randomly driven gas
the granular temperature is {\em different} from that of the driving bath.
Moreover two different granular materials mixed together may stay in a
stationary state with different temperatures. At the same time, granular
temperature determines (as in equilibrium systems) the escape time from a well
in a double well potential.
