Gravitational waves were predicted by Einstein over 75 years ago. Their detection is one of the great challenges of contemporary experimental physics. This Conference intended to honour Edoardo Amaldi for his role in this research and brought together scientists engaged all over the world in gravitational wave experiments with resonant mass, interferometers and space detectors. The book gives a broad view of the detectors presently in operation and of the new generation of interferometric and resonant mass detectors now being built or under design. The book also contains lectures on neutrino telescopes and y ray bursts observations, underlying the role of coincidence experiments among different detectors in opening new windows on the Universe.