Policy Literature, Working Papers, Think Tank Reports (Grey Literature)
Grey literature comprises publications produced by the organization conducting the research rather than by a conventional publisher. They are distributed on a limited basis by the producer of the research or by its funding agency. Like dissertations, they often contain more detailed information than is included in eventual conventionally published work. Sometimes work included in the grey literature is never otherwise published. More information in C. P. Augers’s Information sources in grey literature
GreySource: A Selection of Web-based Resources in Grey Literature lists sources for grey literature (policy reports, technical reports) by general topics
Policy Literature, Working Papers, Think Tank Reports
CIAO (Columbia International Affairs Online) (1991- ) includes articles, books, conference proceedings, working papers, etc.
PolicyFile (1990-) offers public policy reports and studies published by think tanks, university research programs, research organizations including the OECD, IMF, World Bank, the Rand Corporation, and a number of federal agencies.
Policy Archive is a digital library of public policy research containing over 30,000 documents.
Virtual Technical Reports Center offers links to online providers of technical reports.
Think Tank Search - from the Kennedy School of Government, a customized Google search of documents produced by think tanks.
Google advanced search. You can limit by domain: .org
List of think tanks (Think Tanks & Policy Institutes)