I tried out Google Maps Real Estate on Canberra, but this showed too many houses for sale and rent. So I narrowed it down the the suburb, there were still to many, so I tired my street. At this point I discovered the home next door was for sale. This is the first I heard of it. It is a little worrying when you have to look in a global database to find out what is happening a few metres away.
The service lists property and apartments for sale and rent through agencies. There is a page with details for Real Estate Agents to upload my listings to Google. There are two options: Data Feeds or the Google Base API. Data feeds require the supplier to export a file and upload this to Google. The Google Base API provides a more direct, but more technically complex option. There does not appear to be an option for individuals who are just selling one house privately and want to list that. No doubt someone will come up with an ad don service for private sales.