Facebook's own profile search has been bettered by a recent free plugin that has been created in the open source community, check it out here.
Also worth looking at is LinkedIn's new email search agent where you can receive emails when new people enter your 3 degrees who meet your search criteria. There are 3 free searches and you can get more when you have a paid LinkedIn account... check it out at www.linkedin.com/search and edit or cancel them anytime at www.linkedin.com/search?savedSearchListing
