There are many different Search Engines that are used to search the World Wide Web.
Google and Yahoo are both good search engines.
Dogpile is a good choice if you want a metasearch engine (to search several search engines at once).
Often, you will find other connecting links from one website to others that may be relevant to your topic. You should however always evaluate each site as far as its credibility and usefulness in your research. Here are a couple of guides to help:
Internet Information Worksheet