First, you could look at a subject directory. A subject directory is a database of Internet files submitted by site creators or evaluators and organized into subject categories. Subject directories vary so it is best to try several different subject directories. Second, you could use a search engine. A search engine is software that allows you to search for relevant Web sites after entering a term or phrase.
Search engines can be a part of a subject directory or exist alone.
The distinction between subject trees and search engines are becoming blurred as the functions of both are being represented at some sites. The University Library System's Digital Library has a site that lists useful subject directories and search engines. Make sure you type in the exact words and punctuation. For more information on searching the Web, try this Web site from the University of California at Berkeley Library.