Are you looking for someone else's address and phone number? There are many web sites that will gladly supply information to you. In fact, they can supply a lot more information than names, addresses and phone numbers.
The so-called "people search" web sites can help some genealogists but they won't find great-great-granddad. In fact, they won't find anyone who died more than about forty years ago and will provide very limited information about any deceased individuals. However, the "people search" sites are great for finding distant cousins, other people who share your surname, and any other living person you wish to find in the United States.