See newer public LDAP server search page. Use the below if you want to get the hostname, base object, and port for an LDAP server, but the new search is clearly superior.
Other directory services:
Ph directory services page, especially if you know a lot of students, faculty, and staff at colleges and universities (although Ph, like LDAP, can be used by any organization).
Whois lets you look up who owns a domain as well as their contact information.
