There's Nominatim, Data Science Toolkit and the Two Fishes geocoders.

All of this is built on open geospatial data including OpenStreetMap, Yahoo! GeoPlanet, Natural Earth Data, Thematic Mapping, Ordnance Survey OpenSpace, Statistics New Zealand, Zillow, MaxMind, GeoNames, the US Census Bureau and Flickr's shapefiles plus a whole lot more besides. Here's the full list of datasources. https://geocoder.opencagedata.com/credits

I am about to use this for a project so thought I would recommend the find when I saw this post.