YoName – People Search Across Social Networks, Blogs and More
http://www.yoname.com/

People search across social networks, blogs and more. yoName turns your computer into a private detective. Look for anyone you want. You can even look them up by a username or an email address! If they’re on any of the big-time networks like MySpace or Facebook, yoName will find them. This has been added to Finding People Subject Tracer™ Information Blog.