"The Fourth International Conference on Grey Literature (GL '99) in Washington, DC, in October 1999 defined grey literature as : "That which is produced on all levels of government, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers ." including publications by individusla source: http://www.greylit.org/about
Types of Grey Literature list: GreyNet provides a growing list of examples
The New York Academy of Medicine's Grey Literature Report (1999 - 2016) was one of the first initiatives to collect these type of materials at http://www.greylit.org/about . As of January 2017, the Grey Literature Report website and database was discontinued and not updated, but is still accessible.