The Odum Institute for Research In Social Science's Public Opinion Item Index

• Roper Center's ISLA - nonproprietary public opinion data 
• Inter-university Consortium for Political and Social Research (ICPSR) -  data from both individual researchers and most federally funded social science studies 
• North Carolina State Data Center - census data and the National Center for Health Statistics 
• World Fertility Surveys 
• Demographic and Health Surveys (DHS)

The Roper Center for Public Opinion Research
Access to the world's largest collection of public opinion survey data from over 100 countries, documenting over 60 years of commercial and academic surveys.  (Some data only available to UF faculty, students, and staff.)

The Pew Research Center: The People & The Press
Independent opinion research group that studies attitudes toward press, politics and public policy issues.  Known for national surveys that measure public attentiveness to major news stories, and polling on trends in values and political and social attitudes.

CORA, Canadian Opinion Research Archive
Queens University.

European Public Opinion

Public Opinion on Legislative Issues
"A Guide for Class Assignments Beginning with 103rd Congress, 1993" from the University of Michigan Documents Center. 

Public Agenda Online
Nonpartisan briefings on policy and polling --  including digests of news, legislation, and studies, and research studies. Includes great bar graphs and pie charts illustrating public opinion.