The most extensive list of search sites can be found at Beaucoup, which lists links to over 2500 search sites. Most helpful for this class would be Beaucoup's list of General Searchers, Meta and Parallel Searchers, and Reference/Language/Literature Searchers. 

Recent studies identify Google as the best search engines available. You can use Google from this page by typing your search words into the box below.

For helpful information on how to use search engines effectively, see How to Search the Web: A Guide to Search Tools.