"Beyond search engines Yahoo and Google (yes, there is life beyond Google) exist the meta-search sites. These all-in-one search sites save you valuable keystrokes by searching multiple search engines at once and compiling the results for your convenience."
"Sites such as Dogpile, Mamma, and Metacrawler, which harvest results from a number of the Web's best-known large search engines, can be quite interesting. It's intriguing to see how one query can return such different results from various engines. Such variations in results also help illustrate that no one search engine has a monopoly on "knowing" the Web."
"Problem is, regular users of such sites forget -- or don't realize -- that the results they're getting may be skewed. Many search sites these days accept payment from advertisers to list certain Web pages higher in the search results, sometimes marking them as "sponsored" or "partner" links. That means meta-search sites, which tend to give just the first few links retrieved from each engine, are more likely to show sponsored links. Problem is, meta-sites usually strip away any search engine notation that shows that Link X is a paid listing. Users, therefore, generally won't know that on the original search engine, Link X was shown in a colored box or otherwise offset as, in effect, advertising material -- unless they dig deeper to look for sponsorship disclosure information." (from Consumer Web Watch)