Spokeo - A Social Networking Profile Aggregator
The folks at Spokeo call their service a friend tracker; others have called it Spook-eo.
This tool aggregates the activities of your friends from different social networks in one page. Here’s how to get started: You provide your AOL, Gmail, or Yahoo Mail address and password. Spokeo then searches your email contacts (both sent and received). Shortly, a one page listing of your friends’ activities, across over 30 different online applications, will display. Note: The site also only shows information that users have placed publicly on the Internet.
Check out Spokeo's blog for more information.