Evan Miller wrote a wonderful MediaWiki extension to support Google Maps.

<googlemap version="0.9" lat="35.983007" lon="-104.897804" zoom="12"> 36.02439, -104.966125 Wish I was there... </googlemap>

You get this simply enough:

<googlemap version="0.9" lat="35.983007" lon="-104.897804" zoom="12">
36.02439, -104.966125 Wish I was there...
</googlemap>

Bugs

Oddly enough, it seems there's a bug in the distributed files. May be it only affects some implementations. If you see the map in the wiki article, but do see the map in the editor (when you click the icon), try to edit the file GoogleMaps.body.php, and, according to [1], change the line:

     function render16 ( $pContent, $pArgv, &$pParser ) {
to
      function render16 ( $pContent, $pArgv, $pParser ) {

It might still cause problems behind the scene but at least the end user gets to see the map.