Try GeoWhitePages, a bit cluttered but wow powerful (and a bit scary ;)

08.15.2010 >> geowhitepages.com is no longer active.

GeoWhitePages offers users the ability to search and find people geographically. I like the interesting way they’ve combined demographic information and bar charts on the Google Map interface. The information on people digs pretty deep (some will find this a bit scary, however this info is out there on the web already). You can look someone up, click on the person’s name, get more information such as the names of their relatives, and can even link to where you can purchase background checks. You can also search by phone number. From the pop-ups on the map, you can click “show neighbors” and it will return search results showing near-by neighbors and their contact information. To top it off, you can email all search results to a friend :}