People finder?

Does anybody know of a FREE people finder website. I was just wondering because I havent spoken to my mom in a few years. I have tried a few... some will only give me basic info like how old she is and who she has been married to but that is all. I have tried a white pages site.... and it has given me an address with her same name... but how do i really know if that is the right person. She is also unlisted. Would anybody know what a good website is? Thanks..