The General Social Survey is widely regarded as the single best source of data on societal trends. It contains demographic, behavioral, and attitudinal questions, plus topics of special interest. Many of the core questions have remained unchanged since 1972 to facilitate time-trend studies as well as replication of earlier findings. The GSS takes the pulse of America, and is a unique and valuable resource.
The Pew Research Center conducts monthly polls on major policy issues and describes itself as "an independent, non-partisan public opinion research organization that studies attitudes toward politics, the press and public policy issues."
Below is a list of freely accessible websites that compile public opinion data:
The following are links to various major US media outlets' polling divisions.