The book aims to give an overview of the previous Sitges Conferences, which have been held during the last 25 years, with special emphasis on topics related to non-equilibrium phenomena. It includes review articles and articles dealing with new trends in the subject, written by scientists who have played an important role in the development of this area. The book is intended as a commemorative edition of the Sitges Conferences. Graduate students of physics and researchers will find this a stimulating account of the development of non-equilibrium statistical mechanics in the last years, covering a wide scope of topics: kinetic theory, hydrodynamics, fluctuation phenomena and stochastic processes, relaxation phenomena, kinetics of phase transitions, growth kinetics, and so on.