Search all these sites at once:
http://brookings.org
http://heritage.org (Heritage and Nixon Center)
http://rand.org
http://firstgov.gov (Gov Docs)
http://www.cato.org
http://whitehouse.gov
http://whitehouse.gov/omb (Office of Management and Budget)
http://ncpa.org (National Center for Policy Analysis and Debate Central)
http://ucsusa.org (Union of Concerned Scientists)