  The LIGO (Laser Interferometer Gravitational-Wave Observatory) detectors have
just completed their first science run, following many years of planning,
research, and development. LIGO is a member of what will be a worldwide network
of gravitational-wave observatories, with other members in Europe, Japan, and
-- hopefully -- Australia. Plans are rapidly maturing for a low frequency,
space-based gravitational-wave observatory: LISA, the Laser Interferometer
Space Antenna, to be launched around 2011. The goal of these instruments is to
inaugurate the field of {\it gravitational-wave astronomy}: using
gravitational-waves as a means of listening to highly relativistic dynamical
processes in astrophysics. This review discusses the promise of this field,
outlining why gravitational waves are worth pursuing, and what they are
uniquely suited to teach us about astrophysical phenomena. We review the
current state of the field, both theoretical and experimental, and then
highlight some aspects of gravitational-wave science that are particularly
exciting (at least to this author).
