[danpat]

You can type place names into the entry boxes on the front-end - they get converted to lon/lat using a geocoding database.

OR you can drop pins on the map.

[kornish]

Is the geocoding database public as well? If so, do you know where it's hosted?

[maxerickson]

It's https://nominatim.openstreetmap.org/.

There's a use policy: http://wiki.openstreetmap.org/wiki/Nominatim_usage_policy