Google’s Geocoding API limits results to 2,500/day. So what are your options when you hit a geocoding wall with a public/free API?
- Using ArcGIS (or alternatively Gisgraphy, which I have not yet experimented wtih http://www.gisgraphy.com/) you can geocode against the best data you can get your hands on. Esri Streetmaps Data is great, if you have access (as we do at UD). Or you could download public data, like the Census TIGER data, geonames, or an openstreetmap extract for the area you’re interested in, and geocode on these. There is some high quality dataset from cities and states. In the case of Delaware, which licenses TeleAtlas (now TomTom) data, I don’t think non-state users are permitted to use it. I have not seen a way to do this in open source GIS software (e.g., QGIS), which is why ArcGIS or Gisgraphy would be required
- Mapquest/Nomatim (http://developer.mapquest.com/web/products/open/nominatim) and Cloudmade have an unlimited geocoding APIs on OpenStreetMap data. Sometimes that can be slow or inaccurate though.
- Mapquest (non-Nomatim) and Yahoo also have a 5000 result/day limit … a 2x improvement on Google