  This article reviews the physics and technology of producing large quantities
of highly spin-polarized, or hyperpolarized, $^3$He nuclei using spin-exchange
(SEOP) and metastability-exchange (MEOP) optical pumping, and surveys
applications of polarized $^3$He. Several recent developments are emphasized
for each method. For SEOP, the use of spectrally narrowed lasers and Rb/K
mixtures has substantially increased the achievable polarization and polarizing
rate. MEOP in high magnetic fields has likewise significantly increased the
pressure at which this method can be performed, and has led to the observation
of a light-induced relaxation mechanism. In both methods the increased
capabilities have led to more extensive study and modeling of the basic
underlying physics. New unexplained dependences of relaxation on temperature
and magnetic field have been discovered in SEOP cells. Applications of both
methods are also reviewed, including targets for charged particle and photon
beams, neutron spin filters, magnetic resonance imaging, and precision
measurements.
