As participation on our project casastristes.org is growing and people start to incorporate our empty houses map into their sites we now offer a faster way to directly zoom to a city. I wrote a little Drupal module which offers a block on the main page showing a list of available cities. Right now cities are hardcoded and not configurable and maybe it would be nice to integrate that feature in the gmap module but meanwhile I publish the module here. You can see it in action in the right column at the frontpage at casastristes.org named cityzoom.
Here you can download the module: cityzoom
Just put it into your modules directory and activate it, keep in mind that it needs gmap module to work.