  We review the current status and future plans for polarization measurements
of the cosmic microwave background radiation, as well as the cosmology these
measurements will address. After a long period of increasingly sensitive upper
limits, the DASI experiment has detected the E-mode polarization and both the
DASI and WMAP experiments have detected the TE correlation. These detections
provide confirmation of the standard model of adiabatic primordial density
fluctuations consistent with inflationary models. The WMAP TE correlation on
large angular scales provides direct evidence of significant reionization at
higher redshifts than had previously been supposed. These detections mark the
beginning of a new era in CMB measurements and the rich cosmology that can be
gleaned from them.
