geo geospatial documentation modules mapping geocode

I'm looking to add a simple search box (city name OR postcode in same box), which when entered by a user (including anonymous users) will then pass Geocoded data directly to an Openlayers map (or via a View if needs be) for that location. The map will then show a marker on that spot, and will center the map.

Some of my failed attempts include:
- Global Filters module which will work for Post codes only
- Geocoder Autocomplete module which works well for data entry, but I can't see an easy way to Geocode the result as a node to work with Openlayers.

As part of the Geo June activity, we've started a website to aggregate the work being done: http://www.geojune.org. We're aiming to provide documentation, demos of the developing modules, tutorials, etc.