Recent socio-economic trends, such as mounting economic pressure, welfare state reform, the emergence of civil society, and participative democracy, have highlighted the growing significance of the non-profit sector in OECD countries. This sector - often associated with concepts such as the "social economy," "third sector," "voluntary sector," "third system," "independent sector" and, more recently, "social entrepreneurship" - has been facing a number of crucial new challenges. Among these is the drive to introduce rigorous management criteria while maintaining the sector's unique social dimension and fostering social innovation. This publication assesses the new trends in the field of non-profit sector studies. Drawing on contributions from international experts and academics, it reviews the most significant non-profit sector developments in EU countries, the United States, Canada, Mexico and Australia. It also provides a comparative and detailed examination of the tools and methods used to finance, monitor and evaluate this sector of social and economic activity.