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.
MapUSA allows you to map out census data.
One Planet Many People is a U.N. "Atlas of our Changing Environment," which compares and contrasts satellite
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.