Archive of social science data concerning Japan. The SSJDA collects, compiles, and digitizes micro-level data on Japanese society, and offers them for secondary analysis.
Ministry of Internal Affairs and Communication. Check out the "Statistics" tab for access to primary Statistics Bureau surveys and statistical compendia.
The Roper Center for Public Opinion Research is one of the world's leading archives of social science data, specializing in data from surveys of public opinion. The data range from the 1930s, when survey research was in its infancy, to the present. On the Roper iPOLL page, you can search with keywords or filter by country, organization, etc.