I have used wink, zaba, and spock. They each have there +s & -s. For outright phone, address info I prefer zaba, for finding miscellaneous info Wink, but it seems to be less effective over the last 6 months or so. Boolean searches yield better results.
www.123people.com is a great resource to find anyone you want to know more about.
It is also available in 4 languages, English, German, French and Italian.