Gravitational waves were predicted more than 50 years ago by Einstein as a consequence of the general theory of relativity. Because of the weakness of the gravitational interaction, efforts to directly detect gravitational waves have focused on astrophysical sources rather than terrestrial sources. In laboratories around the world, second-generation cryogenic acoustic detectors and laser interferometric detectors are being developed with sensitivity and bandwidth sufficient not only to verify directly the existence of gravitational waves, but also to study the received waveforms. Because the gravitational radiation emitted by an astrophysical source contains information about the source that is orthogonal to information obtained from electromagnetic signals, the direct detection of gravitational waves will open a new window for astronomy. In this review, the likely astrophysical sources of gravitational radiation and the technology of second-generation acoustic detectors will be discussed.