Gravitational waves may reach the Earth in different forms which depend on the nature of the emitting source: they may be short bursts, outcome of a catastrophic event like the gravitational collapse or the coalescence of a binary system; they may be continuous, weak wavetrains emitted by a non axially symmetric, rotating neutron star or by binary systems far from coalescence; or, they may appear as a background created as a polyphonic chorus superposition of different voices: those of populations of astrophysical sources born and evolved in the past, or those coming from matter and energy fluctuations in the first instant of life of the Universe. In this paper we will shortly review some of the most promising astrophysical sources of gravitational waves to be detected by the the resonant or interferometric antennas actually in operation or under construction.