  We give a brief review of some aspects of inhomogeneous viscous fluids in a
flat Friedmann-Robertson-Walker Universe. In general, it is pointed out that
several fluid models may bring the future Universe evolution to become
singular, with the appearance of the so-called Big Rip scenario. We investigate
the effects of fluids coupled with dark matter in a de Sitter Universe, by
considering several cases. Due to this coupling, the coincidence problem may be
solved, and if the de Sitter solution is stable, the model is also protected
against the Big Rip singularity.
