Have you heard about the Invisible Web?
Search engines (like Google, Yahoo!, Bing) only search approximately 20-30% of the web.
The World Wide Web is full of wonderful resources. Use caution, though, when searching. Anyone with a computer can publish something on the internet. Be sure that the web sites and other resources you find are credible. See the evaluation section for more information about how to be more skeptical when using Web Sites as sources.