GSS - General Social Surveys:
The GSS gathers data on contemporary American society in order to monitor and explain trends and constants in attitudes, behaviors, and attributes. Hundreds of trends have been tracked since 1972. In addition, since the GSS adopted questions from earlier surveys, trends can be followed for up to 70 years.
The GSS contains a standard core of demographic, behavioral, and attitudinal questions, plus topics of special interest. Among the topics covered are civil liberties, crime and violence, intergroup tolerance, morality, national spending priorities, psychological well-being, social mobility, and stress and traumatic events.
The GSS is a unique source for sociological and attitudinal trend data covering the United States. It allows researchers to examine the structure and functioning of society in general as well as the role played by relevant subgroups and to compare the United States to other nations.
Coverage: US
ARDA - Association of Religion Data Archives:
This site contains data and information on religion, religious beliefs and compositions, demographic development and more. As a starting point this site only covered US conditions, but now it contains data from almost all countries.
Coverage: US and the world
Pew Research Center:
Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping America and the world. We conduct public opinion polling, demographic research, content analysis and other data-driven social science research.
Coverage: US and the world
Geert Hofstede
contains among other things Hofstede's country comparison