Check out Cyberhomes
http://www.cyberhomes.com/default.aspx
My wife spends lots of time looking at homes through real-estate sites. In fact, almost every night I come home and I found out about where I'll be moving soon 
This site was done by my current company (I'm checking if it's referencable now) and uses AJAX, Live Earth, and real good presentation of information in a nice view.