The Brookings Institution is a research organization that focuses on public policy matters. Provides numerous full-text documents such as policy briefs and articles written by Brookings researchers published in various sources.
The Cato Institute is a free-market oriented research organization that focuses on public policy issues such as social security and international trade. This site provides a large collection of online articles on such topics. Relevant articles can be found by browsing or by utilizing the site-wide search engine.