American Ethnic Geography has maps of ethnic groups, culture regions, reported religions, language, politics, and socio-economics.
David Rumsey Map Collection is a collection of historical maps which can be used to better understand ancetry.
Demographic Data Viewer allows for creation of U.S. maps based on a wide variety of available demographic variables.
Electronic Cultural Atlas Initiative has data and mapping tools, including TimeMap, a free downloadable program that allows for the display of data with respect to time as well as location.
Epodunk has ethnicity maps of the U.S.
Ethnologue contains language maps for most countries in the word.
Jewish History Resource Center: Historical Maps and Atlases has a multitude of links relating to different aspects of judaism, including biblical and cultural maps.
Le Monde diplomatique has thematic maps of political interaction from around the world.
Maplecroft Maps gives users the ability to create global maps with a wide variety of variables, including environmental, economic, political, and social issues. Free registration is required.
Map of Religious Freedom from Freedom House, has maps from 2002 to present and information for each country.
MapUSA allows you to map out census data.
Migration Policy Institute (MPI) Data Hub contains U.S. and global data on migration and immigrant integration.
MLA Language Map is an interactive map that allows straight mapping or comparisons of the prevalence of different languages in the U.S.
National Atlas is part of the Library of Congress' Cultural Landscapes and contains historical atlases and views going back before the 1800's.
Basic Religions Data from Religious Tolerance.org has data and world maps of represented religions.
U.S. Census Bureau Maps and Cartographic Resources has ready made maps featuring information on topics such as congressional districts, census blocks, etc. as well as on-line mapping resources including TIGER Map Server, which allows users to select from many different variables of interest.
U.S. Demographics has maps of the reporting of several major religions from data attained in 2001.