How to Track People Using Social Networking Sites
Share2me is a free browser plug-in that allows you to share your favorite stuff on the Web with your friends across a variety of platforms, with just one simple click.
Yahoo My Web 2.0 Beta Social Search Engine
Yahoo My Web 2.0 is a social search engine, which means that people and search technology are working together to create both better searches and a better search experience.
See How Easily You Can Track Your Friends with Spokeo
Spokeo is a way to track your friends across 22 different social networks so you don't have to visit each one individually.
Upscoop is an intriguing service that allows you to track your friends at various social networking sites, i.e., MySpace, Friendster, etc.