AnyWho. This service from AT&T Labs combines white and yellow pages, maps, e-mail lookup, web page look-up, and reverse look-up into one service. This is a good place to start looking, but use others, too, if you need to, particularly for e-mail and web addresses.
Switchboard. This white and yellow pages directory lists over 100 million names of individuals and businesses, many with email addresses. It licenses the infoUSA telephone databases.
Yahoo! People Search.
This service returns addresses and phone numbers, and includes a separate email search.
The Internet Address Finder. Indexes email addresses for approximately 6.7 million people.
Search MIT's Usenet-addresses database. This utility can find anyone who has posted to newsgroups between 1991 and the present.
Here is a site, Map Quest that will locate addresses on a map for you.