I'm technically off today. But check out HomePages.com.
It's real-estate mapping and accompanying monetization taken to the "next level," with a great deal of local info built around the map. Unlike mashups such as HousingMaps.com, HomePages has complete MLS information.
There were a couple of bugs for me, but it's a very rich product. We'll see a lot more like this soon. Waiting for newspaper-owned HomeGain to do this and then supply that functionality to newspaper sites.