ArcGIS REST API - ArcGIS Services - ArcGIS Server Services Directory REST API
GeoStyler
Generic Styler for GeoData
Boundary Maps for State, County, City & Zipcode | Mapbox
Build boundary map visualizations and perform geospatial analysis with political, statistical, state, city, county, and zipcode boundaries.
The Ultimate List of GIS Formats and Geospatial File Extensions - GIS Geography
The Ultimate List of GIS Formats and Geospatial File Extensions
FEMA Geospatial Resource Center
FEMA GIS supports the emergency management community with world-class geospatial information, services, and technologies to prepare for, protect against, respond to, recover from and mitigate against all hazards.
GeoJSON and KML data for the United States
List federal state county city GIS servers