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' website
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.
February 2011. Photo by Michael Hebb, Flickr.