Meta search engines
§Useful for saving time in searching multiple engines at-once
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§Useful for obtaining an overview of “what’s out there”
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§Beware:  if you enter a complex search strategy, not all of the engines searched may be able to interpret it
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§Try these meta-search engines:
§MetaCrawler Inference Find
§Metafind  Ask Jeeves
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Two important things to remember when using meta search engines:

1.  each meta-search engine searches particular engines.

For example, MetaCrawler searches AltaVista, Yahoo, Thunderstorm, Exite, Lycos, Infoseek & Webcrawler.  It even allows you to eliminate those that you don't want it to search (http://www.metacrawler.com/help/customize.html).  MetaCrawler does NOT search HotBot and many others, however.

2.  The second important thing to remember about meta search engines is that when you enter a complex search, there's no guarantee that every search engine queried will be able to understand the search you've entered.

Take a look at metacrawler, for example:
http://www.metacrawler.com

If you enter (animal rights NOT (dogs or cats)) you'll find nothing from the Metacrawler search.  But if you make a small change in the search format by eliminating the first set of parentheses:  animal rights not (dogs or cats), you will get some results.  But when you analyze those results, you will immediately notice that the NOT was ignored, and you find lots of sites that mention dogs and cats.