Gazetteers

The Columbia Gazetteer of North America
With 50,000 entries, this most comprehensive encyclopedia of geographical places and features will prove invaluable to anyone for whom places hold fascination and who require accurate data about them. It covers every incorporated place and county in the United States, along with several thousand unincorporated places, special-purpose sites, and physical features, as well as Canada, Mexico and the Caribbean.

U.S. Gazetteer
Searchable database, by name or state abbreviation, or 5-digit zip code. Contains geographic information, maps and census data.

USGS Geographic Names Information System (GNIS)
A gazetteer and more! Retrieves detailed information (if available) about a specific place or point of interest (even libraries and parks) in the U.S., territories, and Antarctica. Includes: Elevation, Population, Description, History Notes, Variant Names, and USGS 7.5' Map Names. Can query by Feature Name, County, State, or Feature Type. And, you can bring up maps from the U.S. Census Bureau's Tiger Mapping Service. From the U.S. Geological Survey.
 
Non-US Geographic Names
Information about foreign geographic feature names can be obtained from the GEOnet Names Server (GNS), developed and maintained by the National Geospatial-Intelligence Agency (NGA). The GNS database is the official repository of foreign place-name decisions approved by the U.S. Board on Geographic Names.