Use the Non-governmental Organization Search Engine to search across NGO websites. Sites were chosen based on their consultative status with the United Nations Economic and Social Council (ECOSOC) and also collated from University of Minnesota Human Rights Library, Duke University Libraries' NGO Research Guide, and the World Association of Non-Governmental Organizations (WANGO).
Many fantastic public policy resources--in particular, policy briefs from think tanks, NGOs, and research institutes--can be found online. Here are a few tips for more efficient, effective Google searches:
Include the phrase "policy brief" in your search. (Keep the quotation marks around "policy brief" to find this exact phrase.)
Use a site: search. This will limit your search to a broad domain (e.g., .org sites, .edu sites, .gov sites) or to a specific website (e.g., http://www.urban.org).
If you're not sure which think tank, NGO, or agency might have issued policy papers on your topic, try a search engine that's powered by Google but limited to a select group of sites.