Google (in the US of A) have added Google Real Estate Search to their Google Maps application. Now you can search for real estate in America on Google Maps. The data comes from their Google Base application, however it seems they are going to add data from other sources also. You can try it out by going to http://maps.google.com and then adding (left sidebar) Google Real Estate Search under see more maps!
Here are some articles on this subject:
Google Maps is Going To Be My New Real Estate Search Page
Google Maps Adds Real Estate Search
Another Hint at Google Real Estate?
There are certainly interesting times ahead. I have no idea why Google has not released Google Base in Australia, but they should get their act together and release it shortly. It is not as if it would be a hard thing to do (add country, regions, suburbs) and I cannot wait until it does happen.