  We review sources of high-frequency gravitational waves, summarizing our
current understanding of emission mechanisms, expected amplitudes and event
rates. The most promising sources are gravitational collapse (formation of
black holes or neutron stars) and subsequent ringing of the compact star,
secular or dynamical rotational instabilities and high-mass compact objects
formed through the merger of binary neutron stars. Significant and unique
information for the various stages of the collapse, the structure of
protoneutron stars and the high density equation of state of compact objects
can be drawn from careful study of gravitational wave signals.
