  Beam polarization at e^+e^- linear colliders will be a powerful tool for high
precision analyses. In this paper we summarize the polarization-related results
for Higgs and electroweak physics, QCD, Supersymmetry and alternative theories
beyond the Standard Model. Most studies were made for a planned linear collider
operating in the energy range sqrt{s}= 500-800 GeV. In particular we work out
the advantages of simultaneous polarization of the electron and positron beam.
