http://ds.internic.net/ds/dspgwp.html
This web site provides free access to Internet directory services such as X.500, WHOIS, and Netfind white pages. Through these services, one may attempt to find anyone who is connected to the Internet, using information such as name, geographic location, and workplace or domain. Unfortunately, the interfaces for these tools can be confusing, and some people may be easier to find than others. Note that sometimes the easiest way to find a person's email address is to call them by phone and ask!