Census Boundary & Annexation shps
Census Tiger w/availability info
US Census FactFinder tabular data (use Advanced Search)
American Community Survey or dataferrett
The National Map - Data Delivery
(expand the list in the upper left to access the Download button. It will provide you with multiple download options CSV, GeoJson, KML, and more.
Also, click the gear (Settings) in the upper right to change what earthquakes are visible on the map)
Army Corps of Engineers Public GIS Data
NWS Damage Assessment Tool (view & download)
Ntl Map Small Scale Data Download
Downloading Openstreetmap data
Potential Datasources via openstreetmap
Florida Geographic Data Library
Nebraska Game & Parks Commission
City of Lincoln/Lancaster Co. NE
Montana Fish, Wildlife, & Parks
Milwhttps://sites.google.com/site/mapjab2015/beyond-iowa-gis-dataaukee
GIS Data Repositories Listing (Google Doc)
U of Oregon Resources (has each state's resources)
St. Louis County Minnesota
Los Angeles County California