I would like to announce the new extension I am developing, called
Semantic Google Maps. It is to be a simple extension that does one
thing, and does it good. It builds upon Semantic Mediawiki and
Semantic Forms.

1. Display of coordinates:
The extension provides a parser function that can be used in semantic-
templates. It adds a little map on pages that use these templates. The
parser-function uses the semantic property of type 'Geographic
Coordinates' for centering the map and displaying a marker.

2. Insertion of coordinates:
On the input side, the extension provides a Semantic Forms hack that
adds an extra input type. The input type shows a little map with a
geocoder in your forms to make the insertion of coordinates easier for
users.

1 is stable, 2 is kind of working but still in development.

The choice for Google Maps is arbitrary, the javascript could be
rewritten to another map-api.

If you want extended map functionality, but NOT the two
functionalities talked about above, try Semantic Layers instead.

Semantic Google Maps