National Council on Public Polls (NCPP) - An association of polling organizations in the United States devoted to setting high professional standards for surveys
Pollster.com - Daily poll reports and blog-style commentary on public opinion polling results and procedures.
Public Agenda - Nonpartisan, nonprofit group that tracks public opinion data in the United States
World Public Opinion - The website of a collaborative international project managed by the University of Maryland's Program on International Policy Attitudes. It provides data and analysis of public opinion from around the world on a variety of international political issues.