Built into the listings manager is support for google maps.
The map is located on both the list view and on the individual lisiting pages
In order to make it work for your subdomain you'll need to set up a google map API key for the subdomain name that you set up (IE: yourdomain.virallistings.com ).
It's a very simple operation, you apply for a google maps API key here:
http://code.google.com/apis/maps/signup.html
And then simply enter the API key into the appropriate box on your control panel.

