I have found this very interesting tool by Paul Rademacher . It is an Integration of Google Maps and Craigslist . You can search for housing (rent and for sale) for US cities. It's integrated Google Maps and Craigslist.
Since Google Maps is still in beta version doesn't offer its API, I wonder how Paul has created this tool.
There's also a note on the site: “this site is in no way affiliated with craigslist or Google”
This Google Maps and Craigslits Integration Tool is one of the smartest tools/scripts I've seen for a while.