National Professional Science Master's Association (NPSMA) - NPMSA is a collaborative of national PSM program directors and it works to connect PSM programs with business leaders. Among other things, the association tracks PSM programs, promotes best practices, and hosts a national conference.
ScienceMasters - ScienceMasters provides information on the history of the PSM initiative. It also serves as an archive of PSM reports and statistics conducted by the Council of Graduate Schools and has a PSM program locator that allows you to search by program and by geographical area. There is a lot of good information on this site for students, faculty, and businesses.
Council of Graduate Schools - The Council of Graduate Schools is the national voice for the Graduate Dean community and is an organization that promotes graduate education in the United States. Most US graduate schools are members of CGS. CGS has four basic areas of focus: Best Practices (challenges and effective responses), Benchmarking (data and trends), Public Policy (work with government agencies), and Global Engagement (looking outside the US). CGS publishes yearly reports on PSM programs and their alumni employment levels. CGS hosts annual meetings at national and local levels.
Does a Professional Science Master's Degree Pay Off? - This article discusses the utility of a PSM degree based on the data which were available in early 2012. The bad news is that the data is spotty and incomplete. The good news is that nearly all PSM graduates are employed.
Reports on PSM Enrollments and Degrees - A link to the various reports published by the Council of Graduate Schools on PSM programs and the outcomes of PSM graduates.
Employment Levels for PSM Degree Holders - The latest report on employment for PSM graduates. This report tracks students who graduated with PSM degrees from 2010 to 2013.
NY Times article on the PSM degree - An interesting article in the New York Times on PSM programs. It came out in 2010, so it's a bit dated but is still interesting.