A Non-Exhaustive And Likely To Be Updated List Of Places to Get and Look for Geodata

• Natural Earth: resource for world vector geodata (shapefiles) at 1:10m, 1:50m, and 1:110 million scales.
• OpenStreetMap
  • wiki page on map features: wiki.openstreetmap.org/wiki/Map_Features
  • Overpass for extracting OSM data
• GeoFabrik: shapefiles of different pieces of OSM data carved into pieces
• Metro Extracts: OSM data for metropolitan regional areas around the world, in a variety of formats
• The US Census Bureau's TIGER shapefiles: this is the data that the Census Bureau uses to make its maps.
  • TIGER doesn't come with all that weird Census data that people cite in news stories. To make a map of data like that, you have to join TIGER data to American Community Survey data.
  • Given that government geodata websites are Almost Always The Worst, you might also enjoy Census Reporter.
  • Lots of other kinds of government data can be linked back to Census data, like data from the Bureau of Labor Statistics and the Bureau of Justice Statistics.
• USGS EarthExplorer: Excellent resource for free, awesome satellite imagery. Kind of clunky interface options but um, hi I said free awesome satellite imagery, you'll deal.
• Municipal/state government data portals. For U.S. cities, try Googling the name of any city + "GIS"--for example, here's one for Pittsburgh
• Related Google-fu, a lot of the time if I'm looking for data on a specific topic or subject or region, I try searching that term + "shapefile"--a lot of people doing spatial analysis are still in desktop-land, so a lot of stuff continues to be released as shapefiles.
• OpenAddresses is a repository of address data. Mostly useful if you're compiling your own geocoder (why would you do that) or...IDK, if you like address data.
• The Global Open Data Index (you'll be looking specifically at some of the map-related datasets)