Grey literature exists outside of and is uncontrolled by the usual academic and commercial publishers. It includes conference proceedings, occasional and working papers, policy papers and briefs, hearings, reports, and more.
Columbia International Affairs Online (CIAO)
1991-present; designed to be the most comprehensive source for theory and research in international affairs. Includes working papers from university research institutes, occasional papers series from NGOs, foundation-funded research projects, books, journals, policy briefs, and proceedings from conferences.
1914-present; includes periodicals, books, hearings, reports, gray literature, government publications, and Internet resources. Subjects include politics, public policy, government, international relations, law and ethics, human rights, economics, business, finance, and other social sciences.
Current; indexes research and publications on public policy. Includes links to web resources.
CGS Policy Archive-- collects and archives public policy research publications from US think tanks.
NIRA World Directory of Think Tanks-- indexed by country with descriptions, contact information, and links to organizations' websites.
WWW Virtual Library: Research Institutes-- list of think tank-related links and resources maintained by Wayne Selcher at Elizabethtown College
Public Policy Institutes-- a Yahoo directory of important international think tanks with links to organizations' websites.