Data Gateway provides mostly environmental spatial data for the U.S.

Epodunk has ethnicity maps of the U.S.

Ethnologue contains language maps for most countries in the word.

FEMA

• Map Service Center has flood plain maps

• Hurricane Katrina Flood Recovery Maps contains shapefiles of the affected areas.

MapUSA allows you to map out census data.

National Institute of Justice: Maps

• Crime Mapping on the Web by State

One Planet Many People is a U.N. "Atlas of our Changing Environment," which compares and contrasts satellite
images of the past few decades with contemporary ones

ProvPlan provides tons of maps and data about Providence, RI.

Planning & Development GIS Department for Providence, RI has online maps of zoning, ward, education, etc. for Providence, RI.

ReliefWeb: Map Centre has hundreds of maps of relief work throughout the world, for example about dislocated people in Sudan or reconstruction in Indonesia.