Someone asked how to get the latlong from a specific road near a town on OpenStreetMap.
If you need to do it only once (e.g., you're about to go on a trip, and your GPS cannot find your destination city, but allows you to enter GPS coordinates), you can use Nominatim, OpenStreetMap's geocoding interface.
If you need to do it multiple times, in a programmatic manner, there are at least two ways to do that.
Note: I worked with OSM data a couple of years ago, but I don't have an OSM database on my local laptop right now, so some instructions will be a bit fuzzy. I do apologize in advance.
PostGIS queries on a local OSM DB