http://www.google.com/

If you want to do a focused search on a specific topic, then "google" it. Google is a search engine that uses link relevance; it returns popular websites that meet your search criteria. However, keep in mind that Google doesn't think about your keywords; it does a literal search on the terms you enter. 

http://www.yahoo.com/

Yahoo! is a subject directory. In other words, it helps you find quality information on a given topic or subject. The web sites returned by Yahoo! are associated closely with the keyword(s) you enter.

http://www.dogpile.com/

Much like a dogpile, you can find a number of things using this metasearch engine. A dogpile search crosses several different search websites such as Google, Yahoo!, Live Search, Ask, and About. Dogpile is a good tool for doing a broad search on a topic. But beware--because a Dogpile search spans several search websites, it may take longer to get your results.