open source gis - Reverse Geocoding Libraries

I'm new to GIS and mapping services.

Can anyone tell me what my options are for reverse-geocoding libraries, other than nominatim? I'm most likely going to be working with OpenStreetMap data. So I'll be on the PGSQL/PostGIS stack. Does any of them support the notion of "radius" in their search (which standard Nominatim doesn't support)?

Answer

If you don't want the hassle of managing the entire OSM dataset required for worldwide address datasets you'll need an online service.

As well as Nominatim, Cloudmade have a geocoding API to work with OSM data. There are reverse geocoding examples here. It includes a distance parameter to allow radius searches. E.g.

http://geocoding.cloudmade.com/8ee2a50541944fb9bcedded5165f09d9/geocoding/v2/find.js?object_type=cafe&around=51.51558,-0.141449&results=5&distance=500

If you aren't tied to OSM then have a look at the Google Reverse Geocoding service and example. The docs state it searches within a "tolerance" but then neglects to say what this tolerance is.