If you're trying to find someone in the United States or Canada, you've probably used most of the free "white pages" sites and come across a lot of sites that tease you with a number of results but then want to charge you to see them.
There's another free people finder available now that you might want to give a try. It's called LookupWho.com.
You enter the name, city and state - or as much as you know, with only the last name as a required field - and it provides a list of matches, up to 50. Add more information to narrow down your choices. The results bring up addresses and phone numbers.
LookupWho.com also offers a reverse phone search, useful for when you get an unknown phone number on your caller ID - or when you find an unidentified number on your phone bill.